Three empirical studies comprising this dissertation were carried out to provide a more comprehensive understanding of concurrent measures of both predictors and outcomes of young adolescents' sibling interactions. The participants included older siblings (M age = 14.3), younger siblings (M age = 11.6), and their mothers from approximately 450 families who completed web-based surveys.Study one examined correlates of overt and relational aggression between young adolescent siblings. Family environment emerged as an important factor in explaining internalizing problems as well as overt/relational aggression for both younger and older siblings. Findings also provided partial support for the positive linkages between young adolescents' aggression and their own and siblings' internalizing problems above and beyond family and maternal variables. The main purpose of the study two was to investigate self-criticism as a potential mediating factor in the link between mother-child relationships and aggression or perceptions of social competence. Maternal self-criticism strongly corresponded to the quality of relationships with children, and an intergenerational similarity of self-criticism, particularly for older children, was found. Mother-child relationships and adolescent self-criticism were significantly related to aggression and perceptions of social competence. In addition, the link between mother-child relationships and aggression or social competence is mediated, in part, by self-criticism in adolescents. Using social control theory and attachment theory as guides, study three examined how qualities of young adolescents' social relationships (i.e., mother, sibling, and friend), and dynamic interactions among characteristics of those relationships, are associated with school involvement and delinquency. Results were largely consistent with tenets of social control theory and attachment theory. Young adolescents' social relationships were associated with their adjustment in ways that are protective or beneficial. Furthermore, these social affordances worked additively and in compensatory ways to promote positive adjustment. Positive relationship qualities tended to amplify other relational influences promoting successful development, and these findings were invariant across gender.While optimal mother-child relationships are central in nurturing the child's capacity to develop warm and harmonious sibling relationships in both a direct and an indirect manner, there is a considerable contribution of siblings to adjustment and socialization above and beyond the effects of mother-child relationships.

A primary task of adolescence and young adulthood is to form and develop healthy romantic relationships. While the importance of sibling and romantic relationships have been examined separately, only recently have researchers begun to explore links between the two. The purpose of the present study was to investigate the connection between romantic competence and sibling relationships, especially sibling warmth and sibling conflict, as well as the role of sibling gender constellation in college-aged young adults. This study aimed to examine (a) whether there is an association between sibling relationship quality, such as sibling warmth and sibling conflict, and perceived romantic competence, and (b) the role of sibling gender constellation on the relationship between sibling relationship quality (sibling warmth and sibling conflict) and perceived romantic competence among undergraduate students. Correlation analyses indicated there was no statistically significant correlation between sibling warmth and perceived romantic competence (p > .05), whereas sibling conflict was statistically negative correlated with perceived romantic competence (p < .01). While sibling gender constellation did not have an interaction effect with sibling conflict on perceived romantic competence, which means sibling gender constellation did not have a moderating effect on the relationship between sibling conflict and perceived romantic competence. Limitations and applications of the present study were also discussed.