Abstract
Parents compare their children to one another; those comparisons may have implications for the way mothers and fathers treat their children, as well as their children's behavior. Data were collected annually for three years with parents, firstborns, and secondborns from 385 families (Time 1 age: firstborns, 15.71, SD = 1.07, 52% female; secondborns, 13.18, SD = 1.29, 50% female). Parents' beliefs that one child was better behaved predicted differences in siblings' reports of parent-child conflict. Additionally, for siblings close in age, mothers' comparisons at Time 1 predicted youth's problem behavior at Time 3 through siblings' differential conflict with mothers. The results support and extend tenets from Social Comparison and Expectancy Value theories in regards to social comparison within families.