Freud has left us a theory of fraternal rivalry from his self-analysis. For him, the fraternal is the paternal displaced. Conflicts born of fraternal rivalries are related to the Oedipus complex. Lacan has shown how jealousy between brothers and the conflicts of rivalry have as much to do with a mental identification as with a vital rivalry. The rival plays, in effect, the role of an identificatory image that allows the subject to be constituted. The question of narcissism, particularly the narcissism of small differences, appears as central. How do small differences call into question the ideal ego of the group and the ideal passed on from generation to generation? How can the origin be shared? These are the questions that this article proposes to examine in discussing the works of a number of authors, in particular those of Gilbert Diatkine and Daniel Sibony.