The article aims at studying how the structuring game of aggressive movements is disturbed in the sibling relationship with an autistic person. After a theoretical reminder on the distinctions between violence and aggressiveness, we show from clinical examples which the violence specific and inherent to the autistic pathology constitutes sometimes an obstacle to the creation of the sibling link, by arousing at the siblings feelings that it is difficult to them to admit in them. Then, we explain in what the process of identification, pivot of the construction of the sibling link, is profoundly perturbed by the autism, pathology which is hardly representable: the siblings having difficulty in recognizing in this brother so strange a fellowman. Finally, we investigate the interest of a therapeutic work for the sibship.