1. Introduction

Parental mental illness affects the entire family system (Noller, 2012) and, consequently, the distinctive relationships between siblings (Aldercotte et al., 2016). This article examines how young adults who grew up with mentally ill parents retrospectively interpret their childhood experiences, reconstructing the transformation of sibling roles from the perspective of adult siblings’ shared and differentiated biographies. Siblings often constitute central sources of emotional support and lifelong companionship (Conger & Little, 2010), and although their significance for individual life trajectories is well established, their role in coping with chronic family adversity remains comparatively underexplored (Bossek, 2022; White & Hughes, 2018). Growing up with mentally ill parents confronts siblings with complex and enduring challenges that generate distinctive family constellations, yet these dynamics have rarely been analysed with a systematic focus on sibling relationships (Jungbauer, 2016). It is likewise insufficiently understood whether and through which processes siblings from strained family constellations develop divergent or complementary roles over time (Witte, 2018). Given the centrality of sibling relationships for children's emotional and social environments (Bossek, 2022), as well as their potential significance for coping with parental mental illness (Gutmann, 2008), further systematic investigation is warranted. Drawing on qualitative data from young adults in Germany and Austria, this study therefore addresses the following research question: What meanings do young adults from families with two mentally ill parents attribute to their sibling relationships, and how are these shaped by systemic-dynamic processes? To answer this question, this article examines the interactive negotiation of sibling roles from an interpretative perspective (Soeffner, 2004), with particular attention to the meanings attached to sibling relationships and experiences. The focus lies on both the dynamic emergence and transformation of these roles from an interactionist perspective and the systemic-dynamic processes that structure, coordinate, and stabilise them over time. Based on this analysis, the article introduces the concept of sibling+ role dynamics, highlighting how siblings extend beyond conventional role expectations by assuming compensatory and substitutive responsibilities in families affected by parental mental illness. Methodologically, the study employs fine-structural and systems analysis (Froschauer & Lueger, 2025), enabling the empirical capture of both subject-dependent meaning structures—namely siblings’ lived experiences—and subject-independent process dynamics, referring to structural patterns and relational dynamics within the sibling system.

2. Background

In order to analyse the negotiation of roles in sibling relationships, it is first necessary to clarify the structural characteristics and dimensions of meaning that fundamentally shape such relationships. It is important to emphasise that sibling relationships are invariably embedded in familial contexts, particularly within the parent–child relationship (Whiteman et al., 2011). This embeddedness becomes especially relevant when a parent has a mental illness, as it can substantially shape the dynamics between siblings and, in turn, pre-structure their negotiations of roles. Moreover, social norms and cultural ideals surrounding siblinghood influence these negotiation processes (Gulløv & Winther, 2021). Aspects such as closeness and distance, comparison, age differences, and mutual support constitute central dimensions of sibling relationships. They provide key frames of orientation within which roles are interpreted, affirmed, or transformed, and must therefore be considered as contextual conditions. Finally, it should be noted that role negotiations are biographically embedded and subject to change over time (Edwards et al., 2005). As the present analysis draws on the biographical narratives of young adults, the transition to adulthood must be understood as a transformative moment in the development of sibling roles. The act of narration itself can also stabilise or reinterpret sibling roles and is thus part of the negotiation process (Soeffner, 2004). The following considerations therefore serve to contextualise the empirical findings presented later and to elucidate the conditions that are central to understanding role negotiations in sibling relationships.

2.1 Structual characteristics and dimensions of meaning

Sibling relationships constitute complex social bonds shaped by social class, cultural context, gender, age, and birth order (Punch, 2008). They emerge from the dynamic interplay of familial, individual, and structural conditions (Padilla et al., 2021). Due to their long-term nature, siblings develop an intimate knowledge of one another’s lives (Kibria & Wigen, 2025). While often informal, these relationships involve a tension between obligation and individual agency, producing both positive and negative outcomes (Punch, 2008). They are neither inherently lifelong nor invariably supportive (Blake et al., 2023). Nevertheless, siblings typically maintain sustained contact and exhibit positive affect in their interactions (Spitze & Trent, 2006). Sibling ties influence everyday life, self-construction, and the negotiation of role responsibilities (Davies, 2015, 2023). They act as sites for gendered social learning (Edwards et al., 2005), transmit family values (Gillies & Lucey, 2006), and facilitate the exchange of material, emotional, and social resources (Wyn et al., 2012). These enduring patterns shape both lived experiences and retrospective interpretations of sibling roles (cf. Davies, 2019). In doing so, they provide an analytical lens through which shared and differentiated sibling+ biographies can be reconstructed.

Sibling roles are not fixed; they are socially constructed and continually renegotiated through interaction (Blumer, 1986; Davies, 2019). Biological kinship alone does not determine the meaning of these roles; rather, siblings occupy roles through validated social interactions (Blumer, 1986). Roles develop interactively and remain open to negotiation over time, rather than being predetermined (Finch & Mason, 1993). Analysing sibling roles as flexible and negotiated allows insights into both shared and differentiated biographical trajectories among siblings. Sibling relationships are emotionally ‘sticky’ and deeply embedded, influencing how responsibilities are negotiated (Davies, 2019; Smart, 2007). This embeddedness is reinforced by domestic proximity, behavioural patterns, educational trajectories, sibling reputation, normative expectations, and birth order (Davies, 2019). The distinctive adhesive quality of sibling relationships can render them among the most enduring and intimate bonds in an individual’s life, even when siblings grow increasingly estranged over time (Davies, 2019; Gilligan et al., 2020).

Sibling roles are inseparable from broader family dynamics (White & Hughes, 2018). Parental mental illness shapes parent–child interactions, which, in turn, influence sibling relationships and emotional experiences (Hank & Steinbach, 2018). Estrangement or conflict among siblings often mirrors family structures characterised by distancing or strategic alliances (Blake et al., 2023). Supportive sibling bonds can buffer children from parental conflict, whereas strained relationships may exacerbate stress (Davies et al., 2019; Bossek, 2022). Shared family knowledge reinforces a sense of belonging, while power dynamics among siblings remain informal, context-dependent, and negotiated through compromise or resistance (Punch, 2008; White & Hughes, 2018).

Parental mental illness often involves atypical behaviours that impair daily functioning, provoke psychological distress, and jeopardise well-being (Alle, 2024). Children are at heightened risk of neglect or psychological abuse, including rejection, belittlement, isolation, and manipulation (Plattner, 2019; Lenz, 2012). Individuals affected by such circumstances frequently report severe, chronic, and comorbid parental mental illness, creating critical conditions for the transformation of sibling roles (Lenz, 2012; Plattner, 2019). Parents may struggle with impulse control, emotional regulation, empathy, and communication (Alle, 2024; Lenz, 2012), resulting in diminished parental competence and disrupted parent–child interactions (van Santvoort et al., 2014). Siblings often respond by extending their roles beyond conventional expectations, adopting compensatory or caregiving functions (Bossek, 2022). These adaptations exemplify sibling+ dynamics and illustrate how siblings actively co-construct both shared and differentiated biographical trajectories in response to systemic family challenges.

2.2 Frameworks of orientation in negotiation process

Parents and social norms crucially shape sibling relationships, particularly in negotiating roles (Gulløv & Winther, 2021). These norms—shaped by legal frameworks, media, and personal experience—establish ideals for interaction and function as social scripts within families (Bossek, 2022). When expectations, such as solidarity or aligned attachment, are unmet, social sanctions or familial tensions may arise (Bossek, 2022). For example, there is a normative expectation of shared caregiving for parents throughout life (Towers, 2023). However, moral expectations are not automatically realised: although ideals—such as supporting younger siblings—exist, behaviour is largely determined by the quality and dynamics of actual relationships (Finch & Mason, 1993). Normative expectations are therefore negotiated and adapted in everyday family interactions (Finch & Mason, 1993). Examining how these ideals are internalised and contested illuminates how siblings continuously redefine their roles.

In negotiating roles, the ambivalence of sibling relationships must be acknowledged, as closeness and conflict coexist independently (Campione‐Barr & Killoren, 2019; Hayden et al., 2023). Cohabitation can provoke anger, frustration, and vulnerability, yet also foster love, loyalty, and security (Gillies & Lucey, 2006). Competition, envy, and jealousy often accompany care, affection, and social closeness, which remain central to the bond (Kreuzer, 2016). Despite conflict, sibling relationships frequently exhibit stability and serve as enduring social resources (Aldercotte et al., 2016). Conflict may enhance social skills but can be stressful, particularly when emotional security is threatened or younger siblings are perceived as burdens or scapegoats (Brück, 2019; Reininghaus & Jungbauer, 2016), alienation may arise from favouritism, abuse, or intra-family tension (Blake et al., 2023). Family difficulties and external factors, including socio-economic status and cultural background, shape bonding and empathy (Gungordu et al., 2022). Close, affectionate, and communicative relationships support healthy development, well-being, mental health, self-esteem, academic achievement, and mitigate depressive symptoms (Conger & Little, 2010; Jensen et al., 2023; Kramer et al., 2019), with maximal closeness fostered through open, authentic communication (Padilla et al., 2023). Recognising the coexistence of conflict and closeness clarifies how siblings navigate tensions and negotiate roles to maintain emotional security and mutual support.

Similarity and difference are central to negotiating sibling roles, framing how children and adolescents reflect on self-concept, individuality, group membership, connectedness versus separation, and dependence versus independence (Edwards et al., 2006). Sibling comparisons are embedded within family structures and reveal inequalities (Davies, 2015; Kibria & Wigen, 2025). Relationship dynamics differ in families with multiple children or wider age gaps (Kara et al., 2023), with greater spacing potentially benefiting younger siblings through less constrained resource distribution, influencing educational and developmental outcomes (Steelman et al., 2002). Eldest siblings often assume greater responsibility, youngest siblings enjoy advantages, and middle children may be disadvantaged, denied privileges granted to the others (Davies, 2019; Veith, 2000). Birth order and age hierarchies are fluid, continually negotiated through everyday interactions (McIntosh & Punch, 2009). Information of this kind regarding birth order, age differences, and sibling comparisons illuminates how individuals negotiate roles, responsibilities, and positions within the family hierarchy.

Sibling roles are characterised by mutual support, particularly when parents experience psychological difficulties (Borchet et al., 2020). They provide guidance, including educational and everyday assistance, though relationships may also entail conflict (Davies, 2019; Gillies & Lucey, 2006; Aaltonen, 2016). Support is predominantly offered by older siblings, especially in contexts of limited social resources (Davies, 2019; Lindell et al., 2015). Older siblings transmit insider knowledge, facilitating social capital transfer, yet may constrain younger siblings’ initiatives (Holland, 2009; Aaltonen, 2016). Adolescents observe older siblings’ decisions and achievements, shaping their own trajectories (Davies, 2019). Through caregiving, responsibility-taking, and informal parenting, siblings strengthen family cohesion (Schmolke, 2019). Their relative power legitimises authority while enabling care provision (Mauthner, 2005). These patterns of support illuminate how siblings negotiate authority, caregiving, and reciprocal obligations.

2.3 Biographical embeddedness and narration as a constitutive moment of role formation

With regard to the negotiation of sibling roles, it should be noted that sibling relationships are dynamic, evolving with age and upon leaving the parental home (Edwards et al., 2005). This is particularly pertinent, as the following section examines young adults’ retrospective perspectives on their sibling roles, thus making it necessary to take the transition into adulthood into account. The transition to adulthood, along with the formation of romantic partnerships and career developments, further shapes these dynamics (Conger & Little, 2010). Geographical distance reduces opportunities for visits, support, and communication (Spitze & Trent, 2018), with girls tending to maintain contact via telephone, whereas boys often discontinue shared activities (Edwards et al., 2005). Strong bonds formed in childhood do not necessarily prevent later estrangement (Blake et al., 2023). While conflicts generally decrease during the transition to adulthood, negative interactions may persist (Lindell et al., 2015). Frequent contact can also evoke memories of stressful family experiences (Jensen et al., 2020). Sibling relationships are closely intertwined with shared childhood experiences, which can be critical in shaping relationships in adulthood; these shared memories influence both the perception and evaluation of the relationship (Luotonen, 2024).

As elaborated below, this study elicits the perspectives of young adults through biographical narratives, while also highlighting that narratives themselves play a role in the ongoing negotiation of sibling roles. Family stories, collectively told and transmitted—particularly among siblings—mutually shape their identities (Davies, 2015). The self is not to be understood as a fixed entity, but as something continuously constructed and enacted in everyday life (Holstein & Gubrium, 2000). Narratives play a pivotal role in this process: the ways in which siblings narratively articulate their relationships contribute significantly to the construction and stabilisation of their roles (Soeffner, 2004). Social orders are therefore not static givens, but arise in communicative processes through which they are interpreted, negotiated, and consolidated (Soeffner, 2004). Identity, likewise, is not a pre-existing attribute but is actively produced through everyday narration (Holstein & Gubrium, 2000). This highlights that siblings cannot be examined in isolation but must always be analysed within their relational contexts (Davies, 2015). The recurrent construction and retelling of family narratives may thus be understood as a mechanism that both produces and reproduces the significance of siblinghood (Davies, 2015). Narratives thereby function as structuring devices of social order, contributing simultaneously to the stabilisation and transformation of social roles (Soeffner, 2004).

3. Methodology

3.1 Data

As part of an interpretative-hermeneutic research approach, biographical-narrative interviews (Schütze, 1983) were conducted with 11 adult children of parents with mental illnesses from four German-speaking families. The parents themselves were not interviewed. The interviews were conducted in a one-to-one format, with a comprehensive discussion preceding each interview to explain the study’s objectives, anonymisation procedures, the right to withdraw, and the intended use of the collected data. These details were documented in a written consent form, which was signed by the participants. Two individuals preferred a digital interview via Zoom, while the remaining participants selected their interview location. Following Kara and colleagues’ (2023) recommendation to examine siblings from the perspective of their memories, interviews began with an open-ended invitation to recount their life story without interruption: “Please tell me your life story; take all the time you need. I may take brief notes and ask follow-up questions later, but I will not interrupt”. Follow-up questions were guided by topics raised by participants, including family dynamics, parental illness, coping strategies, and significant life events. The interviews lasted one to two hours, were recorded, transcribed, and analysed using fine-structure and system analysis according to Froschauer and Lueger (2025), enabling an in-depth exploration of adult children’s experiences in relation to their siblings.

Participant recruitment commenced in 2023 through my personal network using a snowball sampling approach. I requested my contacts to forward my enquiry to their acquaintances, encouraging them to further disseminate it within their circles. In this manner, my contact details were shared, and potential participants became aware of my study through their trusted contacts before reaching out to me. A central criterion was that all participants identified themselves as children of two parents with mental illness and named at least one person in their social environment as a sibling. In this study, siblings are defined as anyone whom participants themselves regard as a brother or sister, irrespective of whether they are biological, half-, or adoptive siblings. I set an age range of 18 to the mid-30s for participation. This ensured, on the one hand, that they were able to provide informed consent independently and deliberately, and to discuss potentially burdensome topics autonomously (Pohling, 2021). On the other hand, their childhood and adolescent experiences—including their educational experiences—were still comparatively salient, as not too much time had passed since then.

My research process followed a cyclical design, which meant that data collection extended over several months. In total, six individuals responded to my call for participants. However, during the preliminary telephone interviews, it became apparent that one of these individuals had no siblings and another was a minor at the time of data collection. Both were therefore excluded from the study. With the remaining four participants, the subsequent steps unfolded as follows: I conducted an initial interview and analysed the collected data. The first sibling who contacted me acted as the initial point of contact and was asked to pass on my contact information to their siblings, with the explanation that I was conducting a study on children of parents with mental illness. Siblings were invited to contact me directly if they were interested in participating. Once I had interviewed all interested siblings within a family, I analysed their responses before selecting the next family to be included in the study. The aim was to capture a broad spectrum of perspectives. Accordingly, the study considered a range of parental mental health conditions, diverse socio-economic backgrounds, varying levels of education, and different genders of the participants. During the course of the study, it became evident that all four initially contacted individuals met the inclusion criteria and were subsequently included in the data collection. All siblings from the four families were interviewed, except for two cases. In one case, the youngest sister did not participate. In another family, the youngest sister withdrew her consent shortly after the interview, leaving a total of eleven interviews for analysis.

All eleven respondents identified each other as siblings, without differentiating between biological, adoptive, or half-sibling relationships. This is noteworthy, given that in one family the youngest child was adopted, and in another, the two older siblings had a different father than the younger ones. Nevertheless, the biographical narratives reveal that all participants were raised together during periods that were meaningful to them. The participants reported that their fathers suffered from mental illnesses such as narcissistic and borderline personality disorders, depression, post-traumatic stress disorder, and substance use disorders. Their mothers were diagnosed with conditions including substance-induced schizophrenia, post-traumatic stress disorder, depression, eating disorders, schizoaffective disorders, and anxiety disorders. The following overview presents all potential respondents, indicating their participation in the interviews, as well as their age, gender, and educational background.

3.2 Ethical considerations

Throughout the research process, multiple ethical considerations were carefully addressed, encompassing the following aspects: Participant selection was based on the age of majority to ensure that individuals could provide legally valid, autonomous consent and engage in the study in a reflective and informed manner. Inclusion was determined by participants’ self-identification as children of parents with mental illnesses. Parental diagnoses were not verified, in order to preserve the participants’ perspectives and to prioritise their subjective experiences over clinical classifications. To uphold participants’ autonomy and mitigate potential pressure between siblings, individuals were invited to share the researcher’s contact information with their siblings at their discretion; no sibling contact details were requested or obtained. The researcher did not share any information about what siblings had disclosed in their interviews, nor did participants ask about such information. Based on the intensive preparatory discussions, it became clear that, for the eleven participants ultimately included in the analysis, participation had taken place without any pressure from siblings. The majority of participants reported not discussing interview content with their siblings.

During the initial meeting, participants were briefed on potential emotional challenges and reminded of their right to withdraw from the study at any time. Each participant was asked whether they were currently engaged in psychotherapeutic treatment and whether they could discuss their participation with their therapist before and after the interview. This applied to 10 of the 12 participants, while the remaining two were provided with information on anonymous, no-cost counselling services. Consequently, all participants had access to therapeutic support, helping to minimise emotional distress and ensure appropriate avenues for assistance.

Data analysis was conducted exclusively on anonymised transcripts. Access to the data was restricted to the author, and all materials were stored and maintained in compliance with GDPR regulations. To protect participants’ identities, no full biographical details were disclosed. Only selected statements were quoted, without enabling identification of any individual. Accordingly, the quotations presented below, translated verbatim into English by the author, are annotated solely with participants’ gender to preserve anonymity.

3.3 Analysis

The interviews were meticulously transcribed (Froschauer & Lueger, 2025), treated with the utmost confidentiality, and fully anonymised to ensure the protection of the respondents (von Unger, 2018). The primary objective was to conduct a comprehensive analysis of the participants' statements. An interpretative-hermeneutic approach was adopted to capture latent meanings and structures of significance—those not immediately apparent without interpretation (Soeffner, 2004)—which shape the respondents' lifeworlds (Berger & Luckmann, 1969). This approach is founded on the premise that objective structures of a latent framework of meaning exist, which remain relatively independent of the individual motives and intentions of the respondents. The analysis aimed to identify meaningful patterns within the lifeworlds of siblings and to reveal their interconnections without seeking quantification or representativeness.

Two methodological approaches were combined: fine-structure analysis and system analysis (Froschauer & Lueger, 2025). These methods facilitated both the exploration of respondents' intentions and the analysis of social meanings and the dynamic patterns of interaction within sibling relationships (Froschauer & Lueger, 2025). By integrating these methods, it was possible to investigate both the subject-independent process structures of the siblings' social system and the internally differentiated positions of individual siblings within these structures. The methodological approach led to the reconstruction of social constructions of reality concerning the respondents' personal and structural affiliations. The core focus of the analysis was to elucidate the rules governing the respondents' behaviour and the conditions that gave rise to these rules.

The analysis followed a circular research process in which data collection and interpretation were interwoven (Froschauer & Lueger, 2025). Initially, a small corpus of material was examined using fine-structure analysis (Froschauer & Lueger, 2025), after which system analysis deepened the findings and tested initial assumptions (Froschauer & Lueger, 2025). The results of both methods were consolidated and reflected upon in interim conclusions (Richards, 2015), before the cycle recommenced. Fine-structure analysis allowed for a precise examination of short text passages. Relevant interview excerpts (maximum 10 lines) were broken down into small, meaning-bearing units and subjected to in-depth analysis (Froschauer & Lueger, 2025): a) Paraphrase: How can the unit be summarised? b) Intention/Function: What is the underlying intent of the statement? What function does it serve? c) Latent Meaning: What implicit structures and action implications can be discerned? d) Role Distribution: What attributions and relationship structures are reflected? e) Continuity Options: What possible continuations emerge? Following the fine-structure analysis, a reflective phase ensued before the entire interviews, including previously analysed passages, were evaluated using system analysis (Froschauer & Lueger, 2025). The objective was to reconstruct social and cultural interrelations. To this end, the interviews were divided into thematic units (approximately half a page) and analysed based on the following questions: a) Paraphrase: How can the unit be summarised? b) Context of Expression: What situational and structural conditions influenced the statement? c) Context of Impact: What implications arise for the social field, the respondents' actions, and systemic dynamics?

Since sibling relationships are complex and change over time and across contexts, their analysis is inherently challenging, and no single theory can fully capture all developmental, family, and group-related dimensions (Whiteman et al., 2011). To address this complexity, the data were analysed from an interpretative-hermeneutic perspective, complemented by several guiding assumptions. It was assumed that social phenomena do not simply exist, but emerge through daily interactions: actions become habitual, evolve into established rules and structures, and thus reality is socially constructed (Berger & Luckmann, 1969). Society may appear as a fixed reality to the individual, yet it simultaneously originates from the respondents’ subjective ideas and actions (Döbler, 2022). From this standpoint, the meanings that respondents themselves assign can be captured. According to Blumer, meanings emerge in social interaction, are collectively perceived, and are continually reinterpreted (Carter & Fuller, 2016). Respondents act according to the meanings that objects or situations hold for them, and these meanings are shaped through interaction with others and are constantly evolving (Blumer, 1986). Behaviour is therefore the individual response to one’s own interpretation of a situation and cannot be predicted solely from general knowledge of typical reactions (Carter & Fuller, 2016). Analytically, this requires adopting the respondents’ perspectives and using their own categories to capture the meanings embedded in social interactions (Carter & Fuller, 2016). Understanding sibling relationships thus entails tracing how respondents interpret situations, make sense of experiences, and shape their actions in interaction with their siblings (Carter & Fuller, 2016). Reality is understood as emerging, developing, and taking shape within respondents’ interactions with their siblings (Prus, 2008). These considerations allow sibling relationships to be viewed not as static, but as dynamic, with meanings that continually evolve through the interplay of subjective experiences and social processes. Since biographical narratives formed the basis of the data, it was necessary to consider that social order—including roles and norms—is stabilised, negotiated, and interpreted through storytelling (Soeffner, 2004). Accordingly, respondents’ knowledge is regarded as a dynamic, interpretative process negotiated through social interaction (Soeffner, 2004). The way respondents describe their relationships contributes to the construction, transformation, and stabilisation of their roles. Overall, these assumptions enable the identification of the meanings that respondents attach to their sibling relationships in their narratives.

4. Results

To examine how siblings in families where both parents experience mental illness negotiate roles within the sibling group, and to elucidate the systemic dynamics that shape these negotiations, it is first essential to specify the significance of parental mental illness for sibling relationships, and to articulate how respondents perceive and inhabit these relational contexts. The participants’ accounts correspond closely with the effects of parental mental illness documented in the existing literature, underscoring the analytical importance of their experiences and providing the foundation for the subsequent analysis of sibling role negotiation processes. The circumstances outlined in Part 2, and the interactions they engendered, shaped the respondents’ everyday realities. These realities, in turn, fundamentally mould both the character of sibling relationships and the processes through which roles were negotiated and enacted within the sibling group. In the following presentation, respondents are occasionally referred to in the plural; this should not be interpreted as suggesting uniformity of experience across participants, nor as implying any quantitative prevalence. Rather, plural formulations indicate recurring patterns and tendencies discerned across the interviews, revealing the relational dynamics that shape the negotiation of sibling roles.

4.1 Parental mental illness affects sibling relationships

The respondents’ accounts illuminate how their everyday realities are shaped through interactions with their mentally ill parents, highlighting the pivotal role of sibling relationships in this process. As one respondent reflected, “we knew there were these siblings, and we weren’t imagining it, but it’s real, and at least we’re not alone”, highlighting how siblings provide an essential reference point for mutual recognition and collective resilience. Parents’ behaviours, which respondents often experienced as unpredictable and potentially consequential, were interpreted as a constant threat to their own existence. This perception profoundly shaped their actions: a central feature of their behaviour was the imperative to protect themselves from possible adverse parental reactions. This protective imperative not only structured individual conduct but also served as a foundational reference point in the collective negotiation of sibling roles.

The narratives indicate that siblings negotiated their roles in relation to one another in ways that allowed them to cope most effectively within the collectively experienced threat. Parents were positioned—implicitly but persistently—as the source of danger, whereas siblings were perceived as allies. This dynamic rendered sibling relationships a central resource for maintaining a sense of stability, as illustrated by one respondent: “But I think we were really the only support we had, because there was always this omnipresent feeling of shared suffering”. The shared experience of the situation, the collective suffering, and the recognition of the unavailability of protective parental support made siblings appear as the sole reliable sources of protection. Consequently, sibling cohesion became a foundational element of their everyday orientation.

This continuous interaction gave rise to an unspoken sibling code, evident in everyday life without ever being explicitly articulated. It primarily encompassed mutual protection, loyalty, solidarity, and defence. Its authority did not derive from formal rules, but from the repeated experience that siblings had to bear joint consequences and were therefore mutually dependent. This code remained fluid: its significance was continuously affirmed, negotiated, or contested in practice, depending on how siblings interpreted each situation and the expectations they held toward one another.

The material demonstrates that sibling relationships in the studied context constituted an ongoing negotiation process, in which closeness, responsibility, and loyalty were continually renegotiated. The initially observable cohesion did not remain stable in every configuration. Particularly when one sibling—often the youngest, who shared fewer experiences with the others—perceived that better protection or fulfilment of needs could be obtained through a closer bond with a parent, the established interaction patterns were altered. In such cases, orientation toward parental attention gained prominence, prompting the child in question to strive to maintain their status as the “favourite” child. This is illustrated by the respondent’s statement: “But my brother knew it because he, like, found her, and um, in the end, he betrayed me, um, so that I got my ass beaten again.” Here, the respondent experienced how her brother betrayed her for his own benefit, and she had to endure the resulting negative consequences. This action was accompanied by a break in the sibling alliance, creating a new interpretive framework in which the perceived protection offered by a parent appeared more effective than that provided by siblings. This placed a noticeable strain on the sibling structure, as the familiar joint front disintegrated, requiring participants to realign their positions relative to one another. These moments reveal the sensitivity and significance of the ongoing interpretations and counter-interpretations through which siblings organised their relationships and shaped their family life.

At the same time, it became evident that parents actively intervened in this structure by assigning specific roles to their children, which could continue to influence sibling interactions. Respondents described how certain children were explicitly designated as favourites and granted privileges. However, the acceptance of this special status was often experienced as a source of guilt within the sibling relationship, as it entailed an imbalance that all parties felt and accounted for in their behaviour. Furthermore, children were entrusted with responsibilities that, in their own estimation, they were neither capable of fulfilling nor would have assumed voluntarily. Parental statements emphasizing one child’s responsibility for the well-being of another gained particular weight when an incident occurred, such as an accident during play. Children interpreted such situations as implying that they indeed held far-reaching responsibilities and adjusted their behaviour toward their siblings accordingly. This is illustrated by the following statement from one respondent, made after recounting a highly delusional experience with his mother: “A world collapsed inside me. I was desperate and didn't know what to do next. I knew that I had lost her somehow, and I didn't know how to deal with my little [siblings], who had been sitting on the sofa for days watching Disney videos with me”. This clearly demonstrates that the respondent immediately assumed the role of being responsible for his sisters and considered how to protect them. The roles assigned by parents thus became action-guiding frameworks that carried over into everyday interactions and had a lasting impact on the siblings’ relationships.

In retrospect, some respondents interpreted these experiences as deliberate attempts to set the children against one another. They reconstructed how both they themselves and their siblings had been placed in positions that served less to foster sibling cohesion and more to fulfil parental interests. The following statement by one respondent further illustrates that, in hindsight, siblings recognised and understood breaches of loyalty toward one another: “What the hierarchy among us children is, and accordingly, if you grow up in such strange circumstances, or in, in such difficult circumstances like we did, then of course, these children also make use of these roles. Why? Because they just, because if one child is safer in its assigned role than the other, then that child is not going to risk its own safety just because it loves its sibling”. These interpretations indicate that siblings did not merely experience familial dynamics passively, but actively endeavoured to make sense of them. They contextualised their experiences, drew connections between the roles assigned to them and the tensions these created in sibling relationships. In this way, it becomes evident how participants constructed their reality by attributing meaning, questioning it, and reshaping it—and how their sibling relationships were continuously transformed through these processes.

The interviewees’ accounts clearly illustrate the profound impact of their parents’ mental illnesses on everyday life, continuously engendering a sense of emotional distance in family interactions. The children consistently experience a lack of attention, recognition, and reliable affection, prompting their behaviour to be strongly oriented toward fulfilling this fundamental need for closeness. Their narratives reveal repeated efforts to establish a connection with their parents in day-to-day interactions, even as they are confronted with rules whose logic is largely opaque to them. The significance of adhering to these rules in relation to the need for parental affection is evident in one respondent’s statement: “There was always this fear that if you didn't/uh, didn't/uh, what's the word? (...) if you didn't live up to your father's expectations, he would abandon you and no longer want any contact”. These rules are set and modified by the parents and are confirmed or revoked in the course of family interactions, yet they appear fragile and heavily influenced by the illness from the children’s perspective. Because the children encounter such rules only within this specific relational context and do not encounter them outside the family, the rules appear irrational and difficult for them to evaluate.

Within this uncertain framework, siblings develop their own mechanisms for orientation. They observe one another closely, use each other as reference points, and continuously negotiate how to respond to parental demands in their collective actions. Particularly when certain rules are perceived as arbitrary, a space emerges in which siblings must weigh loyalty to one another against the hope of securing parental affection. This dynamic is especially evident in situations where children either “cover” for or betray one another. Most respondents describe prioritising the sibling code—that is, maintaining sibling solidarity—even when a betrayal could temporarily enhance closeness to the parents. Simultaneously, some narratives indicate that, at specific moments, individual children relinquish this loyalty. In these cases, the respondents interpreted interactions with the ill parent as more promising and aligned their behaviour more closely with seeking parental approval than with sustaining sibling bonds. Consequently, relational lines within the sibling group shift, and the significance of the sibling code is renegotiated on a case-by-case basis.

This dynamic becomes particularly salient during periods of acute parental illness. Respondents describe such situations as crisis-like, highly disruptive, and characterised by considerable uncertainty. One respondent provides an example of such a crisis: “He took it out on all of us, so if it was, um, violent outbursts towards my mother, where we children were always afraid, would he kill her or not? Or if it was towards us siblings”. Under these conditions, sibling bonds tend to intensify, as the children perceive the family situation as threatening and construct a shared protective space through mutual support. However, this protective space is not a static structure; it is continuously reinterpreted and reinforced through ongoing interaction. Conversely, when the parents stabilise, respondents perceive the situation as less stressful, and their attention shifts accordingly. Siblings increasingly focus on their individual life trajectories, while the immediate salience of their relationship diminishes. This pattern becomes especially apparent during the transition to adulthood, when young adults move out and establish physical distance. As distance from the parental home increases, the perceived threat diminishes, rendering sibling protection less central.

At the same time, respondents emphasise that the experiences shared during these periods constitute a lasting foundation for sibling bonds, as illustrated by the following statement: “Um, accordingly, this situation still connects us today, and we still maintain a/ a relationship that I really, really value”. Even when their life paths diverge in young adulthood, sibling closeness remains available as a resource. When a new parental crisis arises and the perceived threat intensifies, siblings tend to draw closer again. This produces a relational network that oscillates between individual development, everyday distance, and situationally heightened solidarity, in which siblings continuously negotiate how they support one another and co-construct their shared reality.

4.2 System dynamics –sibling+

Role shifts emerged in the respondents’ narratives as a central dimension of the everyday negotiations within sibling relationships. They became particularly salient when a parent’s mental illness created a tangible void in family life—a void that the siblings were compelled to address collectively. In such situations, respondents repeatedly described how certain siblings assumed positions that exceeded the boundaries of a conventional sibling relationship. The resulting role configuration can be conceptualised as sibling+, as it incorporates elements of parental caregiving practice and integrates them into sibling interaction. These shifts did not occur as fixed, one-time reallocations; rather, they unfolded as ongoing, situationally reconstituted points of orientation within the family context. The siblings experimented with and gradually consolidated their altered role understandings through everyday interaction, with some increasingly perceived as central figures of support. At the same time, these assumptions of responsibility reshaped the structure of sibling relationships in lasting ways: As sibling+, some siblings became a form of functional parental substitute for the others, without fully transitioning into a parental role. It was especially in routine activities—where decisions needed to be made, conflicts mediated, or emotional security provided—that the effectiveness of these role shifts became evident and generated new orientations for all those involved.

The account of one respondent, whose older siblings had taken on such functions, illustrates the experienced significance of these processes: "So without my […] older siblings—so they were really, uh, I don’t think exactly a replacement for mother and father, but really, um, very important when you basically don’t have mother and father, I mean, when you have a mother who actually behaves like the child." When she notes that her siblings were “very important when you don’t really have a mother and father,” she highlights how the siblings created forms of reliability through shared practices—forms otherwise missing in the family constellation. By simultaneously emphasising that this was “not really a substitute for a mother and father,” she delineates the boundary between the formal parental role and what is actually accomplished within sibling interaction. This tension reveals how respondents interpret their lived reality: sibling+ compensate for the loss of parental functions without themselves becoming “parents.” Their altered role understandings thus develop not only in response to the parent’s illness but also within the process of joint action, through which meanings are negotiated and relationships are correspondingly reshaped. Through these narrative reconstructions, respondents stabilise their interpretation of the family configuration and render intelligible how they addressed the perceived parental void through sibling practices.

In the respondents’ everyday family life, the role of the sibling+ emerges as a relationally constituted and continuously negotiated outcome of joint interactions. The narratives illustrate how siblings negotiate meanings in situations where parental mental illness is perceived as a limitation on parental responsibilities, resulting in shifts in their positions within the sibling hierarchy. Respondents describe how certain tasks, originally designated as parental responsibilities, are redistributed among siblings through collaborative action. When daily care and family stabilisation are deemed necessary, individual children assume responsibilities they themselves regard as originally parental. However, these shifts are described not as permanent states but as context-dependent responses to perceived crises.

The role of the sibling+ manifests as an expanded position of responsibility, encompassing both emotional and practical dimensions. It includes educational tasks, the provision of trusted support, role modelling, and the furnishing of security and guidance for siblings. Respondents do not take these responsibilities for granted; rather, they view them as necessary for maintaining family structures when parental functions are compromised. Simultaneously, the sibling relationship persists as an emotionally anchored bond, such that role shifts remain tied to shared experiences and the other siblings’ willingness to acknowledge them. Only through this interactive process can a sibling truly assume the role of sibling+; unilateral attribution or decision-making is perceived as neither possible nor legitimate by respondents.

This role is assumed only in situations where the parents’ condition is perceived as critical or unstable, and the siblings collectively determine that a coordinating figure is necessary. Such assessments emerge from exchanges among siblings as they seek to minimise perceived threats to themselves and others. The sibling who ultimately assumes the role of sibling+ is closely linked to perceived competence differentials among the involved parties. In joint negotiations, the siblings assess who possesses the requisite skills to provide guidance and make decisions in stressful circumstances. The sibling deemed particularly capable in this process is granted the authority to take the lead and is recognised by others as superior. This entails a set of expectations: the sibling+ is expected to act reliably, responsibly, and in the best interests of their siblings, while simultaneously being accorded greater influence and educational authority.

However, once the respondents no longer perceive a need for this role, the sibling+ position is renegotiated. Siblings dissolve the temporary hierarchy and return to an equal standing. Consequently, the role of the sibling+ remains tightly bound to situational stress, which endows it with its distinctive character. It differs significantly from everyday mutual support, as it encompasses tasks that respondents clearly attribute to their parents and often experience as overwhelming. At the same time, they describe this assumed role as a central resource during challenging phases of life, providing protection, stability, and guidance to siblings. One respondent succinctly highlights this significance, describing her reliance on the support of her older siblings and the crucial impact of their actions on her own well-being: “Um, with my two older siblings, they play a very important role for me, because I know that without the two of them, um, without this support and, um, a lot of things wouldn’t be the way they are now, like, a lot wouldn’t be as, uh, good as it is now."

For siblings who occasionally assume a sibling+ role for other siblings, acting as a substitute parent in accordance with family role expectations can be quite challenging. This is illustrated by the following statement from one respondent: "I love my brother, of course, I love him very much, and I would also, if he somehow had problems or something, I would always help him, but of course, I also must not make him too soft or anything, but rather make sure that he somehow finds the right path, so kind of, yeah, I am probably rather strict with him, but actually, I just want to help him." The respondent initially emphasises a strong emotional bond and a willingness to help his brother at any time. However, the phrases “I mustn't spoil him” and “I must make sure he stays on the right path” indicate that he views his support not merely as sibling care, but as a form of responsibility that requires regulatory and guiding action. This self-description suggests that, in certain situations, he perceives himself in a role that extends beyond the typical sibling relationship, incorporating elements of parental functions. His statement that he is “somewhat stricter” with his brother exposes a tension: on one hand, he seeks emotional closeness, but on the other hand, he feels compelled to set boundaries and regulate his brother’s behaviour. This underscores the challenge of simultaneously fulfilling two roles that can involve conflicting expectations—the role of a loving brother and that of a controlling, guiding figure. The respondent frames this strictness not as an assertion of power, but as an expression of care. Nevertheless, his explanation demonstrates the extent to which he is guided by familial norms, according to which a responsible individual not only accompanies but also corrects. Moreover, this self-portrayal reveals an implicit power dynamic: by positioning himself as able to determine what constitutes the “right path” for his brother, he assumes a role hierarchically superior to his sibling. Importantly, this assumption does not appear to stem from a desire for dominance, but from a perceived duty arising from the family situation and internalised role expectations. The challenge, therefore, lies in exercising this guiding role without jeopardising the sibling relationship—a balancing act that repeatedly pressures the equality inherent in sibling bonds.

5. Discussion

In the respondents’ narratives, their sibling roles are continually reproduced, stabilised, and woven into broader family histories (Davies, 2015; Soeffner, 2004). Overall, the fluidity of sibling roles (Punch, 2005) becomes particularly evident in the emergence of the sibling+ role in the context of parental mental illness. Meanings are co-constructed in interaction (Finch & Mason, 1993), negotiated and transformed through everyday relational practices; assuming particular roles requires reciprocal recognition (Blumer, 1986). Changes in horizontal sibling relationships are therefore closely intertwined with the vertical dynamics of the parent–child relationship (Kalmijn & Leopold, 2019). This is reflected, for instance, in the respondents’ accounts of parents actively assigning roles — such as delegating responsibility for younger siblings to one child or positioning one child as the preferred “favourite”. These parental attributions intervene deeply in sibling negotiation processes and shape the ways in which sibling roles take form. The respondents interpret such role assignments as an immediate consequence of the parents’ symptoms and connect them to altered parental behavioural patterns.

The respondents describe growing up with parents experiencing mental illness as a recurrently threatening situation, particularly during acute phases of the illness. This sense of threat arises not only from the immediate symptoms but also from parental behaviours and interactions, from which the respondents infer rules that they experience as difficult to comprehend. When these rules are violated—such as by siblings—the respondents anticipate negative consequences. As a result, they must remain vigilant and continually adjust to the parents’ situationally negotiated, modified, and inherently unstable expectations. Because both parents are affected by mental illness, the respondents report an absence of parental protection and increasingly turn to their siblings as the source of safety on which they are most likely to be able to rely. Through jointly constructed interpretive processes, they strengthen their sense of cohesion—particularly during periods of strain—negotiate roles, and adapt them to protect the sibling group as effectively as possible. When the parental dynamics that they perceive as threatening subside, they reorient themselves more strongly toward their individual spheres of life and accordingly renegotiate their roles.

In situations that respondents experience as particularly stressful or threatening, the siblings involved renegotiate their respective roles. The crises associated with their parents’ symptoms generate a shared sense of urgency from which a reorganised constellation of roles emerges. During such phases, sibling relationships function as stabilising resources (Mota & Matos, 2015); the severity of family problems intensifies mutual closeness and empathy (Gungordu et al., 2022). At the same time, acute crises foster especially strong bonds that provide siblings with support in the face of parental mental illness (Bossek, 2022). Against this backdrop, siblings negotiate who will assume particular tasks and responsibilities. In this process, the role of the sibling+ takes shape—offering direction in situations perceived as threatening. The group engages in dynamic negotiations over how to avert the perceived threat most effectively and stabilises those roles deemed necessary. These shifts arise from unmet individual needs and are embedded in culturally mediated notions of motherhood and fatherhood (cf. Davies, 2015). When the perceived level of threat diminishes, the sibling+ role loses its function and the distribution of roles is reorganised once again. Individuals who temporarily assume this role gain greater authority, as their leadership is accepted within the sibling group, even though explicit power is typically considered illegitimate in sibling relationships (Bossek, 2022). The sibling+ role occupies a distinct position in that it entails forms of power asymmetry that differ from parental authority (Punch, 2005), while still constituting a comparatively powerful status. Consequently, sibling relationships—ordinarily characterised by non-hierarchical dynamics (Kara et al., 2023)—become temporarily hierarchical, yet remain structured by reciprocity, fairness, and self-interest (McIntosh & Punch, 2009). Once interactions with the parents are again perceived as stable, authority shifts back to them (Davies, 2015).

The role of siblings+ is shaped by a sense of responsibility that develops early and positions them as central actors in caregiving, protection, and guidance (Gillies & Lucey, 2006). Such responsibility creates opportunities for personal development, as providing direction and support to siblings fosters self-confidence and competence (Borchet et al., 2020; Gillies & Lucey, 2006). At the same time, respondents frequently describe assuming these roles as overwhelming, as it often requires subordinating their own needs. The strong bond is therefore experienced ambivalently—both as an expression of solidarity and as a source of strain (Heenen-Wolff, 2021). The shifts in roles, which align with the perceived symptoms of the parents, suggest that the “adhesiveness” (Smart, 2007) of sibling relationships rests not only in their emotional continuity but also in their capacity to absorb the loss of familial coherence through the redistribution of responsibilities.

The analysis demonstrates that the siblings continuously negotiate their relationship under the conditions of both parents’ mental illness, developing meanings that are intrinsically tied to this familial burden. The parents’ disorders do not simply constitute a contextual backdrop; rather, they structure the ways in which the siblings relate to one another, allocate responsibilities, and define their respective roles. What it means to be siblings in this situation is constituted and reshaped through their joint practices, rendering their relationship a dynamic process shaped by their perception of the parents’ condition. Because severe mental illness in both parents—and its implications for sibling relationships—has received little scholarly attention to date, the findings can be connected only to a limited extent with existing research. However, this low degree of comparability underscores a clear need for further research to achieve a more nuanced understanding of sibling relationships under conditions of significant familial stress. Nonetheless, several limitations must be acknowledged: Its exclusive focus on norms and values in Austria and Germany, combined with a small sample of eleven participants, limits the generalisability of the findings (Towers, 2023). Expanding the sample size and diversity, and incorporating parental perspectives, could yield a more comprehensive understanding of sibling relationships. Compared to other family relationships, sibling ties remain comparatively under-researched, with the literature disproportionately focused on white, middle-class U.S. families (Gilligan et al., 2020); this study similarly focuses on white families. Greater attention to cultural diversity is therefore essential (Song, 2010), alongside consideration of social and historical dimensions such as class, generation, geography, ethnicity, and biological status (Mauthner, 2005). Moreover, the applicability of sibling+ dynamics to other family constellations remains unclear, including the circumstances of role shifts, their occurrence beyond parental illness or absence, and their long-term consequences. Equally, it is important to consider the boundaries of sibling+ roles and the significance of family size for role shifts (Veith, 2000). Only children also merit attention, as they may seek substitutes for the ‘plus’ function and could be particularly disadvantaged by the absence of siblings. Ultimately, institutions and professionals working with families in which parents are only partially able to fulfil their roles must explicitly consider sibling relationships, as only through such attention can the specific needs of affected children be recognised and addressed.