In this chapter, the author looks at writers who share her view that relationships between siblings and peers are to be distinguished from those between parent and child and that they hold a particular and important place in the inner world. The belief that siblings help each other to negotiate oedipal conflict leads M. Kris and S. Ritvo to suggest that the choice of a marital partner is always influenced by the sibling relationship. Siblings can engage in cooperative play as much as aggressive attack and they can become deeply attached to each other. The author argues that Anna Freud’s discovery of the Oedipus complex contributed to the abandonment of the theoretical problem of sibling attachments. In the eighties, at Yale University in the United States, an interest in sibling relationships and their effect upon emotional development was shown. Love and jealousy between siblings is different to the oedipal conflict between parents and children.