`titrebSummary`/titreb This article presents the first hypotheses and questions developed from a clinical study on the representation of the parental function by lesbian couples asking for Artificial Insemination by Donor (aid). The early French speaking and English speaking reference to the debate on same sex parenthood within the psychoanalytical community led us to structure our qualitative data analysis (case analysis of thirty two couples) around two main issues. First, aid can be seen as an experience which introduces a third person to the lesbian couple and carries an important paradox for the psyche of all those involved ; secondly, it is useful to analyse the psychic developments linked to access to same sex parenthood, and in particular how subjects construe themselves as biological or social mothers. This two-pronged analysis based on clinical cases actually serves a metapsychological reflection on the concept of psychic bisexuality as a key element of psychic development for lesbian couples.