The nuclear family, as we used to know it, has been changing for the last several decades. Single-parent families, same-sex parents, blended families, and multiple-parent families are a widespread clinical reality. Can one still speak of “the family” or ought one to speak of “families”? This diversity of contemporary structures leads us to seek out and isolate the common trait to the myriad family forms and permits us to demarcate, beyond this diversity, the hallmark of the family and its psychic function for the subject. In order to isolate this trait, the author departs from two main theoretical premises, which may seem contradictory at first glance against the backdrop of the current scholarship on the history of the family (E. Durkheim and E. Todd). He seeks to resolve this contradiction by introducing the logic of the unconscious and its modality in the formation of structures. The author proposes to consider the nuclear family as an equivalent to the formation of the unconscious, like a symptom or a dream. The family, like the nucleus of the dream, is where heterogeneous elements meet and interact. Thus, like a dream or a symptom, it constitutes a substitute or a solution for the absence of relations between the sexes(Lacan's concept, following Freud). As a result, a family that structures a child, is a framework that originates from the reality of no-relation, which it structures at the same time as covering it. The author shows how contemporary family forms can respond, from a psychic point of view, to this structuring definition of a family.