Perhaps the most obvious feature of the relationship between siblings is its diversity. Sibling relationships differ from peer relationships because of their frequency and amount or interaction; the durability of the relationships; the existence of prescribed roles; accessibility; and the degree of common experience. Conflict between siblings in early childhood may be rivalrous, but it is more productive to emphasize the learning to handle conflicts in the very early years. Affection, reassurance, and companionship are frequently but not always concomitants of conflict in the preschool years. Sibling rivalry does not disappear in middle childhood, although these children increasingly have friends who are important to them and have an arena other than the family in which to establish themselves. In adolescence, sibling relationships are powerfully influenced in the areas of achievement and success; sexuality and beauty; and social relations with peers, outsiders, and other siblings. It is during late childhood and adolescence, when the forging of adult sexual identity becomes a primary task, that siblings have the greatest influence on one another. Although the parents play the primary role in influencing the child's sexual identity, siblings can have some effect on how the individuals complete their development. Relationships between siblings can be considered dysfunctional when they prevent the developmental progress of the children or interfere with family functioning consistently over a long period. Intervention and non-intervention in sibling disputes by parents both have their problems. The best results occur when parents are at ease with their own sexuality, have a good sexual relationship and keep communication channels open. (ABL)