Siblings are often children’s first play partners since about 80% of Western children have a brother or sister with whom they are close in age. The sibling relationship is an important context for young children’s learning and development because in the early childhood years, siblings spend more time with each other than with parents or other children. Sibling relationships are also affectively intense, involuntary, and lifelong relationships. This relationship is characterized by both reciprocal (equal and returned) interactions such as during play and conflict and also by complementary (hierarchical) interactions that define teacher–learner interactions. Reciprocal interactions, particularly play and prosocial exchanges, are important for children’s development and by age 3, siblings strongly prefer to play with each other rather than with their parents.

Play is considered ...