Siblings
Dear RP friends,
We continue our blog articles on the Psychology of Close Relationships, the official Research Programme Theme for 2025/2026.
In this review, we delve deeper into sibling relationships. In our announcement of the Research Program 2025/2026 (Hugs and Hypotheses: Psychology of Close Relationships), we noted that birth order can influence relationships, making it an important issue to discuss with clients on the couch and to examine scientifically.
Alfred Adler was one of the first theorists to connect birth order with client understanding. Adler highlighted psychological birth order, focusing on children’s perceptions of their family roles over their ordinal positions. He stated, “It is not the child’s number in the order of successive births which influences his character, but the situation into which he is born and how he interprets it.” However, research has mainly focused on ordinal birth order, frequently overlooking second-born children. Furthermore, in research, lifestyle traits correlate with birth order: firstborns typically achieve highly, only children usually seek success, middle children are sociable, and youngest children show significant social interest. Overall, studies indicate that birth order affects relationships, with individuals frequently forming connections with those of the same birth order, leading to more same-birth-order friendships and romantic relationships.
Eckstein et al. (2010) found that first-born children often achieve the highest academic success due to their motivation and leadership qualities. They are highly affiliative under stress and are overrepresented in educational and professional settings. Even though they typically conform to parental values, they may also display less conventional sexual behaviours and take risks. Notably, the arrival of a sibling can lead to feelings of dethronement for first-borns.
Only children often possess unique traits. They often display high intelligence, have a strong need for achievement, and commonly pursue higher education. However, they may experience more behavioural problems than their peers. Socially, they have a lower need for affiliation and are sometimes perceived as selfish. While they may have more psychiatric disorders, they are seen as likable, cooperative, and trusting, typically with a clear sense of gender identity.
Middle children often feel a lack of belonging within their families, influencing their social interactions. They are sociable, exhibit fewer behavioural problems, and are well-adjusted. In team sports, they relate well to peers, and their competitiveness may manifest differently than older siblings, favouring stability and relationship commitment.
Youngest children tend to display high social interest and agreeableness and are often seen as the most rebellious and empathetic among siblings, leading to challenges like alcoholism and psychiatric disorders. They are drawn to artistic pursuits rather than scientific ones. A significant age gap may make them act like an only child, while a smaller gap may induce anxiety like that of the oldest sibling.
The authors conclude that beliefs about birth order can influence behaviours and career choices and that Adlerians do understand family dynamics based on children’s ages and sexes, which aids in family counselling (Eckstein et al., 2010).
Furthermore, sibling relationships, viewed through a self-psychology lens rooted in Alfred Adler’s work (Hart, 2021), significantly shape identity and emotional growth. While siblings offer vital support, the common experience of idealizing them can create rigid, all-or-nothing perceptions, hindering emotional flexibility. Healthy development involves moving beyond these idealizations to appreciate individual differences. Clear parental boundaries enable siblings to explore their distinct traits securely, fostering mutual respect and cooperation, which lessens rivalry. Navigating sibling bonds requires balancing the desire for “twinship”—shared understanding and similarities—with the reality of individual differences in age, personality, and interests. Parental support in acknowledging each child’s uniqueness and encouraging authentic connection through shared experiences is crucial for a lasting and supportive sibling relationship (Hart, 2021).
Moreover, college life can strengthen sibling bonds, as highlighted in a qualitative study of 18 sibling pairs attending the same college (Younkin et al., 2021). The study revealed three key themes: shared loyalty, where siblings actively support each other; a closer connection, marked by renewed appreciation; and increased openness and sharing of personal experiences. This supportive dynamic provides crucial emotional backing during the uncertainties of emerging adulthood, often surpassing even friendships. Based on family systems theory, positive sibling relationships during college can have lasting benefits, although future research should explore this in more diverse contexts (Younkin et al., 2021).
One longitudinal study (Amici et al., 2022) revealed that high maternal stress, especially from environmental and prenatal factors, is linked to more behavioural problems (like anxiety and hyperactivity) in children, a trend that persists throughout childhood. However, older siblings offer a protective buffer. They help reduce these issues in younger siblings by providing emotional support and boosting social interaction, even when mothers experience high stress. This sibling support might be even stronger in cultures with close sibling bonds. The study underscores the critical need to manage maternal stress during and after pregnancy and highlights the value of long-term research in identifying key times for intervention (Amici et al., 2022).
A large study of Shanghai preschoolers (Wu et al., 2022) found that having older siblings boosts psychosocial well-being and school readiness compared to being an only child. Interestingly, having younger siblings didn’t show significant differences. The research indicates that socioeconomic factors and parent-child interactions are crucial, and that siblings do not hinder development, potentially alleviating parental concerns. Fostering supportive family environments and positive older sibling relationships is beneficial, and policymakers should consider interventions to support families, especially those with lower socioeconomic status, to enhance child development (Wu et al., 2022).
Another fascinating longitudinal study (Paine et al., 2021) highlights how sibling and friend relationships are key to children’s development of humour, a stable social trait. Observing 65 sibling and friend pairs aged 4-7, the research found that second-born children often produce more humour than first-borns. Humour was categorized into seven types, from silly actions (“Performing Incongruities”) to playful language (“Word Play”) and even rule-breaking (“Taboo”). Interestingly, humour production was consistent whether kids were with siblings or friends. Sibling interactions act as a “natural laboratory” for social learning, especially in sound play and banter, which helps build skills for positive friendships later. While factors like birth order (second-borns being funnier) and sibling dynamics influence humour, significant gender differences weren’t found in this age group. The stability of humour production in early childhood underscores its role in building social skills and relationships, and this research highlights humour’s importance in development and its ties to sibling and friend interactions (Paine et al., 2021).
Conversely, one study (Shivers et al., 2023) reveals that siblings of individuals with mental illness (MI) and suicidal ideation (SI) face increased burden and distress, and closeness doesn’t always ease these feelings. Findings highlight the unique challenges these families face, emphasizing the need for tailored therapeutic approaches and more research across diverse populations over time. The study found that the emotional strain of a sibling’s MI/SI can overshadow even close bonds, and the desire to protect oneself might lead to distance. Strategies to help these siblings include open communication, psychoeducation about MI/SI, self-care, support networks, family therapy, destigmatizing mental health, and encouraging individual professional help. Future research should delve deeper into the complex link between sibling closeness and burden, consider cultural influences, use longitudinal studies to track changes, combine research methods for richer insights, focus on specific mental disorders, and examine the impact of family therapy (Shivers et al., 2023).
One systematic review (Murphy & Bush, 2024) explored how the COVID-19 pandemic impacted adolescent relationships with siblings, peers, and romantic partners. Interestingly, sibling relationships often improved or stayed stable, especially for older teens and girls, while peer connections generally weakened due to social distancing. Romantic relationships saw varied experiences, with some feeling closer and others more isolated. The review stresses that age, gender, and culture played a role in these shifts and emphasizes the need for more research to better support adolescent mental health during stressful times. Notably, siblings became crucial in coping with peer isolation during lockdowns, particularly for girls aged 12-15. While close sibling bonds were sometimes linked to increased problem behaviours under COVID stress, older adolescents generally had more positive sibling interactions, while younger ones faced more conflict. Increased family chaos led to more sibling conflict and less closeness, yet siblings provided vital support, especially for younger teens, boosting their well-being (Murphy & Bush, 2024).
In conclusion, the multifaceted nature of sibling relationships profoundly impacts individual development and well-being across the lifespan, as highlighted by various studies. From Adler’s early insights on birth order and its correlation with personality and relationship choices (Eckstein et al., 2010) to the nuanced influence of idealization (Hart, 2021), college proximity (Younkin et al., 2021), maternal stress (Amici et al., 2022), socioeconomic factors (Wu et al., 2022), and even humour development (Paine et al., 2021), the sibling bond presents a rich area for psychological inquiry. Furthermore, the unique challenges faced by siblings of individuals with mental illness and suicidal ideation (Shivers et al., 2023) and the adaptive role of siblings during crises like the COVID-19 pandemic (Murphy & Bush, 2024) underscore their significance. Future research should prioritize longitudinal studies across diverse cultural and socioeconomic contexts to fully understand the long-term and varied impacts of sibling dynamics. Investigating specific mechanisms of influence, particularly in mitigating stress and fostering resilience, and exploring effective intervention strategies for families navigating complex sibling relationships, remain crucial avenues for advancing our understanding and supporting individual and relational well-being.
Eckstein, D., Aycock, K. J., Sperber, M. A., McDonald, J., Van Wiesner III, V., Watts, R. E., & Ginsburg, P. (2010). A review of 200 birth-order studies: Lifestyle characteristics. Journal of Individual Psychology, 66(4).
Paine, A. L., Howe, N., Gilmore, V., Karajian, G., & DeHart, G. (2021). “Goosebump man. That’s funny!”Humor with siblings and friends from early to middle childhood. Journal of Applied Developmental Psychology, 77, 101321.
Amici, F., Röder, S., Kiess, W., Borte, M., Zenclussen, A. C., Widdig, A., & Herberth, G. (2022). Maternal stress, child behavior, and the promotive role of older siblings. BMC Public Health, 22(1), 863.
Younkin, F. L., Firmin, M. W., Belles, A., Hardman, M. L., Holloway, M. E., & Patrick, D. R. (2021). Sharing life together: Siblings relationships while attending the same college. Personal Relationships, 28(4), 927–939.
Hart, C. (2021). “I Am You and You Are Me”: A Self Psychology Perspective on Sibling Relationships. Psychoanalytic Social Work, 28(1), 64–85.
Shivers, C., Russon, J., Benson, M. J., King, A., & Textoris, S. (2023). Siblings’ role positions and perceptions of mental illness. Contemporary Family Therapy, 45(3), 360-370.
Wu, S., Zhang, D., Li, X., Zhao, J., Sun, X., Shi, L., … & Jiang, F. (2022). Siblings and early childhood development: evidence from a population-based cohort in preschoolers from Shanghai. International Journal of Environmental Research and Public Health, 19(9), 5739.
Murphy, L., & Bush, K. R. (2024). A systematic review of adolescents’ relationships with siblings, peers, and romantic partners during the COVID-19 lockdown. Current Psychology, 1–17.