Brothers and sisters of adults with mental retardation: gendered nature of the sibling relationship.

Differences and similarities between brothers and sisters of adults with mental retardation with respect to the instrumental (caregiving, companionship) and affective (positive affect, emotion) aspects of the sibling relationship were examined. Sisters scored higher than brothers in the caregiving, companionship, and positive affect aspects of the sibling relationship. Brothers' sibling relationships were conditioned by the gender of the sibling with mental retardation. Brothers of brothers with mental retardation had a more favorable emotional response than did brothers of sisters. Two-wave longitudinal data showed that sibling involvement and closeness increased over time, but was dependent upon changes in the health of the mother. The findings are discussed in relation to normative patterns in the sibling relationship across the life course.