In this article, the concept introduced by Lyman Wynne, that the individual develops epigenetically within the family system, is discussed and validated with data from a study of the characteristics and relationships of 27 women with borderline personality disorder and their parents. Each stage of the epigenetic process is impaired in one way or another, adversely affecting subsequent stages. Early impairment of attachment-care-giving processes is at least partly attributable to a lack of empathic parenting; effective communication is married by family members' inability to experience or express feelings (alexithymia); this, in turn, makes it difficult to engage in joint family problem solving. Mutuality between family members does not occur in such a context, and there is an absence of intimacy between family members. These are often abusive family systems, with multiple abuse and intrafamilial sexual abuse more specifically directed at the daughter with BPD. The symptoms of the daughter can be understood systemically, as representing both predispositional characteristics and reactions to the family system. It is suggested that the epigenetic paradigm could be used to characterize the specific failure of developmental processes in many different disorders.