Family members share space and resources, for instance.
Siblings share the mother's emotions and attention. Similarly, the family educates its young members to master their drives and to postpone the gratification and satisfaction, which attaches to acting upon them. The incest taboo teaches children how to control their erotic drive by abstaining from ingratiating themselves with members of the opposite sex within the same family. Additionally, it probably interferes with the defensive aspects of the family's existence. It is through the family that aggression is legitimately channelled, expressed and externalized.