This study examined the associations between the early family environment, older siblings' early characteristics, and later sibling relationships. Participating were 37 families with infants and preschool-age older siblings who were observed in the laboratory at 3 time points and followed-up 3 years later. Findings indicated that parents' early marital relationship was associated with more positive sibling involvement and teaching, and less sibling conflict and rivalry 3 years later. Fathers who were more controlling of their children's emotions during preschool had children who later demonstrated less sibling teaching. Mothers' sensitivity with infant siblings was associated with positive sibling relations 3 years later, but fathers' sensitivity correlated positively with later sibling conflict and negatively with later sibling teaching. Older siblings who were securely attached to fathers provided more care to younger siblings 3 years later, while older siblings' early emotion understanding was negatively associated with later caretaking. Multiple regression analyses revealed that parents' early marital love and their sensitivity with infant siblings were the most consistent predictors of all sibling relationship measures other than instrumental caretaking. The findings underscore the importance of the early affective family environment in shaping sibling relationships over time as well as the importance of examining both parents' contributions to sibling relationships. (Author)