Siblings Influence on Young Adults' Development: A Three-Study Dissertation

As the longest lasting close relationship, often extending from birth until death, sibling relationships play an important role throughout the life course. To date, however, only limited work has examined the process by which siblings influence each other during young adulthood. Given that developmental differences between older and younger siblings diminish in young adulthood, it is possible that bidirectional (older-to-younger as well as younger-to-older) are more likely as compared to adolescence (in which top-down or older-to-younger influence has primarily been explored). It is further possible that processes of observational learning, including modeling, and sibling differentiation continue into young adulthood, shaping sibling similarities and differences as well as young adults’ overall well-being. This three-study dissertation addressed these possibilities using extant data from three different studies. First, Study 1 examined the potential for bidirectional sibling influence on young adults’ binge drinking, marijuana use, risky sexual behaviors, and volunteering behaviors. Further, this study examined the degree to which sibling closeness exacerbated sibling similarities across these various domains. Next, Study 2 examined whether sibling relationship qualities (i.e., intimacy and conflict) mediated the longitudinal association between sibling differentiation and young adults’ well-being. Finally, Study 3 simultaneously examined whether and how domain specific sibling modeling and differentiation shaped sibling similarities and differences in young adults’ educational attainment, work prestige, and romantic relationship qualities. Across the three studies, findings suggested that through different processes, siblings continue to influence each other during young adulthood. Overall, evidence for bidirectional sibling influence emerged in domains in which development was ongoing for both older and younger siblings during young adulthood (e.g., risky sexual behaviors, romantic relationships); however, ...