--- - |2 This study examined associations between parents’ relationship conflict and parent–adolescent triangulation, and changes in adolescents’ perceptions of sibling affection and hostility. The goal was to learn whether conflict in parents’ relationships spills over to siblings’ relationships, or whether siblings compensate by becoming less hostile and more affectionate. Using a subsample (N = 400) from the Flourishing Families Project (FFP), we found a trend for mother–adolescent triangulation predicting an increase in sibling hostility across 2 years. Fathers’ reports of relationship conflict were related to increased levels of initial sibling hostility, but predicted a marginal decrease in hostility over time. Findings support increased understanding of parenting dynamics associated with changes in sibling relationship quality, and have the potential to inform clinical practice. - Journal of Marital and Family Therapy, Volume 44, Issue 3, Page 527-542, July 2018.