The integrative and assimilatory tendencies of modern society are based on “fraternity”, which refers to the sibling level. Siblings are for each other primary objects with all the possible positive and negative affects that can go along with it. The ego functions are strongly stimulated by the exchange with the siblings, but also the infantile sexuality. In adolescence there can be sexual assaults between sister and brother that are still socially taboo. How does one explain that brotherhood can arise from sibling relations - so often characterized by jealousy and rivalry?