We compared the extent of parents’ differential treatment (PDT) and girls’ and boys’ perceptions of parents’ fairness in middle childhood and adolescence as a function of the gender constellation of the sibling dyad. Further, we examined links between PDT in three domains, parental warmth, parents’ temporal involvement, and the allocation of household tasks, and both siblings’ self esteem and positivity in the sibling relationship. Participants were mothers, fathers and both first- and secondborn siblings from 385 families. To collect information on siblings’ family experiences and well-being, family members were interviewed individually in their homes. During the subsequent 2–3 weeks, 7 evening telephone interviews also were conducted; these focused on siblings’ daily activities. Analyses revealed different patterns of PDT for siblings as a function of age and gender constellation, stronger links with self esteem and sibling positivity for perceptions of fairness than for PDT, and different patterns of association with self esteem and sibling relations across domains of PDT. We emphasize the importance of studying the processes through which PDT experiences have implications for siblings.