<p>Despite the well-established links between coparenting and child behavior problems, little is known about the longitudinal development of dyadic mothers’ and fathers’ coparenting relationships within the larger family context. Informed by family systems theory, this study sought to examine how maternal and paternal coparenting systems were simultaneously manifested over time from infancy (Year 1) to preadolescence (Year 9), and how various antecedents at age 1 were associated with the patterns of dyadic longitudinal coparenting change. Further, we tested whether distinct coparenting patterns were related to later adolescent behavior problems (Year 15) even after accounting for early behavior problems, child gender, and demographic risk factors. This study leveraged the data of the Future of Families and Child Wellbeing Study (<i>N</i> = 3923 families), which oversampled unmarried, low-income, and ethnically and racially diverse families. Growth mixture models identified four trajectory change patterns of mothers’ and fathers’ coparenting (latent classes): (a) <i>both high stable support</i> (69.7%); (b) <i>father less-supportive</i> (15.4%); (c) <i>both decreasing support</i> (8.1%); and (d) <i>father unsupportive</i> (6.8%) coparenting classes. Further analyses revealed that adolescents in the <i>both high stable support</i> coparenting class showed significantly fewer internalizing and externalizing behavior problems at age 15, compared to other classes. Findings highlight dyadic coparenting processes in family systems, which may help inform development of targeted programs to promote adaptive coparenting in mothers and fathers among ethnically, racially, and economically diverse families.</p>