IntroductionFew studies have simultaneously focused on the effects of marital conflict and marital intimacy on adolescent development, and little is known about the role of sibling relationships. Thus, this study examined the association between marital relationships and adolescent behavioral problems, including depressive symptoms and aggressive behavior. At the same time, we explored the mediating role of sibling hostility and sibling affection and the moderating effect of birth order in multichild families in China.MethodsParticipants included 842 adolescents (Mage = 12.60, 46.2% boys) from Henan Province. Marital relationship, sibling relationship, birth order, depressive symptoms and aggressive behavior were assessed by a self-administered questionnaire. SEM was then used to examine the role of sibling relationships and birth order in the association between marital relationship and adolescent behavioral problems.ResultsOur results showed that marital intimacy was negatively correlated with depressive symptoms and aggressive behavior, while marital conflict was positively correlated with them. Marital intimacy was associated with depressive symptoms and aggressive behavior through both sibling hostility and sibling affection. Marital conflict was indirectly associated with depressive symptoms and aggressive behavior through sibling hostility. In addition, the first-born adolescents were more sensitive to marital intimacy.DiscussionGiven that the occurrence of adolescent behavioral problems is more common in contemporary society, our findings suggest that establishing a more intimate and warmer family atmosphere and promoting positive interactions between siblings may help control adolescent mental health problems.