Drawing on 5 waves of multiple-informant data gathered from focal participants and their parents and intimate partners (n = 360 families) who completed annual surveys in the German Family Panel (pairfam) study, the present investigation examined bidirectional associations between the development of adults’ conflictual and intimate interactions with their parents and intimate partners. Autoregressive cross-lagged latent change score modeling results revealed a robust pattern of coordinated development between parent-adult child and couple conflictual and intimate interactions: increases in conflict and intimacy in one relationship were contemporaneously intertwined with changes in the other relationship. Additionally, prior couple intimacy and conflict predicted future parent-adult child relations in 7 out of 14 cross-lagged pathways examined, but parent-adult child conflict and intimacy was only associated with future couple interactions in 1 pathway. These associations were not moderated by the gender of parents or the adult child or whether the adult child was a young adult or nearing midlife. Frequency of contact between parents and the adult child moderated some associations. Adults simultaneously juggle ties with parents and intimate partners, and this study provides strong evidence supporting the coordinated development of conflictual and intimate patterns of interaction in each relationship.