The current study focuses on the effects of sibling gender configuration on family processes during early childhood. In a sample of 369 two-parent families with two children (youngest 12 months, oldest about 2 years older), both siblings’ noncompliant and oppositional behaviors and fathers’ and mothers’ sensitivity and discipline strategies were observed. Both siblings’ aggressive behaviors and empathy of the oldest sibling were assessed with parent-reports. Children in families with two sons showed more problematic interaction patterns compared with children in families with an oldest girl. In families with two boys, older siblings were more aggressive and fathers were less sensitive toward their youngest child in comparison with families with two girls. Furthermore, in boy–boy families older siblings showed more oppositional behavior and younger siblings more noncompliance compared with girl–boy families. These findings highlight the importance of sibling gender configuration in the development of child behavior and parent–child interactions.