This study examined sibling behavior during polyadic family conflicts (involving three or more family members) by identifying operational conflict elements (i.e., roles, topic), power strategies, effective influence of power, and social domain argumentation. Polyadic conflict sequences (n = 210) were identified in 35/39 families with two siblings (aged 4 and 6) and their parents observed at home. The dominant conflict topic, siblings' use of power and power strategy executed in relation to social domain argumentation, revealed unique qualities of conflict in the polyadic family context; effective use of power strategies to facilitate favorable outcomes differed by sibling birth order. Our account presents a nuanced view of the intricacies of polyadic family conflict, which provides unique opportunities for children's learning and socialization by siblings and parents.