Our approach on early bilingualism, focused on transcultural clinical research, shows that the idea according to which children from a foreign background master two languages is not always accurate. The difficulty of language transmission is situated within crossing and complex factors : on one hand, it includes the axe that corresponds to parents'identity projection and their children's affiliation, and, on the other hand, the axe in which the parents are attached to their languages and the children positioning towards these attachments.