Research demonstrates the central role of mother-child relationships in child socioemotional development; however, families are complex systems and the unique roles of multiple family subsystems in early infant development have received less attention. In the present study, we investigated the role of multiple family relationships (interparental, mother-infant, father-infant), during pregnancy and the first month after childbirth, in infant socioemotional functioning at 6months. We administered semi-structured interviews during pregnancy to assess multiple qualities of the interparental relationship. At 1month postpartum, parents completed reports about their feelings and attitudes toward their infant to assess impaired bonding. At 6months, parents provided reports of child socioemotional functioning. Both mother-infant and father-infant impaired bonding were uniquely associated with infant socioemotional impairment, controlling for prenatal interparental relationship quality. Additionally, multiple dimensions of the interparental relationship (i.e., poor-quality conflict management, inadequate support for fathers, and low levels of respect toward mothers) were associated with infant socioemotional impairment controlling for parent-infant bonding. Results also demonstrated an indirect pathway, such that poor sexual quality during pregnancy was associated with fathers (but not mothers) reporting more impaired bonding with their infants, which was linked to greater infant socioemotional impairment. Results highlight the importance of understanding the broad family environment, prior to and immediately following the birth of the child, to identify at-risk children at the earliest possible stages of intervention.