In this small-scale indicative study I explored the issue of individuation in relation to the life stories of a group of adult opposite-sex twins, using a psycho-social approach and a narrative interview methodology (Hollway & Jefferson, 2013). I found that none of the six interviewees reported having had a close relationship with their mother in infancy and childhood but five said they had had a close relationship with their co-twin, which endured in later life. Cleaving to the co-twin seemed to complicate and disrupt identity formation and the development of mature adult relationships. I concluded that the respondents in the study had experienced a similar psycho-social challenge to that of same-sex twins - how to honour their twinship while at the same time attempting to forge a unique identity - but that they seemed to have faced an additional challenge when it came to developing adult relationships with members of the opposite sex.