The current study draws on family systems theory to explore how infants’ joint attachment relationships with their mother and father can be predicted by the prenatal marital quality and contribute to the qualities of the triadic family interactional when children are two years old. Families (N=125) were followed over the transition to first-time parenthood. Couples’ prenatal negative marital affectivity was coded in a dyadic interaction task. Assessments of infants’ attachment to mother and father at 12 or 15 months were used to form four groups of mixed pairs: secure with both parents, insecure with both parents, secure with mother-insecure with father, and insecure with mother-secure with father. At 24 months, triadic (mother-father-toddler) interactions were videotaped and rated on emotionally disengaged, controlling, and balanced family interactions. Infants raised by parents with higher levels of prenatal marital negativity were less likely to form a secure attachment with their fathers (even when they had an insecure attachment with their mother) which, in turn, contributed to less balanced interactions in the triad. On the other hand, when infants developed an insecure attachment with their mother (even when they were secure with fathers), triads displayed significantly more controlling behavior. The gender differences in the current study highlighted the importance of understanding the unique influence of the infant’s attachment relationship with their mothers and fathers.