The coparenting relationship between mothers and fathers is a central feature of family life, however, the coparenting relationship was mostly ignored by family scholars and researchers until at least the mid 1990s. The construct of “coparenting” was usually synonymous with postdivorce coparenting and confined to the study of conflict and cooperation across households. It is only in the past 15 years that both family theory and research directly assessing multiple dimensions of coparenting has exploded. One explanation for the neglect of coparenting (at least outside of divorced families) is that the field is just beginning to absorb family systems theories concepts that are prominent in family therapy. Whereas family researchers in psychology and interpersonal communication were invested in dyadic formulations of family relationships (e.g., husband-wife, parent-child), family therapists have long focused on triadic interactions, claiming that the triad is the minimal unit needed for understanding family communication (Bowen, 1976; Minuchin, 1974). Triads allow for examining the influence of one relationship, such as the mother-father relationship, on a third member of the family, such as a child. A triadic analysis also illuminates how one relationship affects another, such as how the marital relationship affects the father-child relationship. Beyond family therapists, it is only in the past 15 years that family researchers have studied coparenting dynamics intentionally. Even less theory and research has focused on how mothers and fathers coparent multiple children who have relationships with one another (polyadic relationships). Why did triadic, family systems models become appealing to family researchers only during the 1990s? We note that this was the decade of powerful research findings on the negative impact of marital and coparental conflict on parent-child relations and children's well-being in intact families (see review by Erel & Burman, 1995) and of parallel findings in studies of postdivorce families. Beyond the empirical findings, we believe that scholars became disenchanted with the over simplifications of dyadic models of family communication and decided to take the plunge into family systems theory by trying to operationalize heuristically interesting ideas that family therapists had observed but never measured. Jay Belsky (1981) and Patricia Minuchin (1985) were early theoretical leaders in this integration of developmental and family systems theories.