This chapter explores sibling and peer relationships in light of contextual events, particularly those that include parents and caregivers. The literatures on sibling and peer relationships have included attention to the contributions of parental involvement, yet treatments in the two literatures have entailed somewhat distinctive types of approaches and implicit aims. The large body of work documenting the importance of peer relationships to children's mental health and social adjustment has stimulated considerable interest in the foundations of peer friendships. Toward the overarching goal of unraveling the complex social network, a number of studies have examined child development in triadic environments where third parties have sometimes been construed as exerting influences that are indirect. Notions about social competencies such as, sociability, empathy, and social understanding are likely to be advanced, if not reshaped dramatically, by augmenting attention to the child's social functioning in caregiver-child-child contexts.