Scholars have suggested that family life may influence children's attributions about close relationships. Using a sample of 369 two-parent families with 2 children (a target adolescent in the 8th grade and a sibling aged 10 to 18), we investigated whether the sibling's negative attributions regarding the target adolescent were associated with mother's and father's negative attributions regarding the target adolescent, or the gender constellation and birth order of the sibling pair. In addition, we used the self-reported negative attributions of both siblings and adolescents to investigate whether attributions predicted one's own behavior, or whether the behavior of the partner predicted the perceiver's negative attributions. Structural equation models showed that mothers' and fathers' negative attributions regarding the target adolescent predicted concurrent negative attributions for girls, but not boys. In addition, siblings' negative attributions regarding each other predicted their negative and positive behavior toward the partner 2 years later. The positive behavior of the attribution target also predicted the perceiver's negative attributions, but its effect was weaker. Girl sibling pairs were less negative in their attributions than cross-sex sibling pairs and boy sibling pairs. Finally, although younger siblings were less negative in their attributions than older siblings, this difference decreased over time. This study advances the knowledge of negative attributions in close relationships by identifying family correlates of an understudied, but important, close relationship.