When you cannot be the same. The twins as emblematic case of the identity construction by difference composition within the family

Bringing empirical data to support the hypothesis that the development of personality, according to a constructionist and relational approach, is a function not only of the genetics and of the shared and unshared environment, but also of the "positions" taken in the semantic dimensions relevant to someone’s own relational context (MacIntyre, 1981; Ugazio, 1998) is extremely important for the therapist of any theoretical orientation. To achieve this we investigated the case of twins as emblematic of this process: just as genetics make identical two or more members of the family system, differentiation processes become more forceful to ensure the necessary individualization of each one. So we interviewed 25 pairs of parents of twins (half dizygotic, half monozygotic; 2-10 years). The qualitative analysis of the interviews indicate that parents of monozygotic twins perceive, on the abstract level, their children as more similar to each other than the parents of fraternal twins. However, the parents of monozygotic parents refer more relevant differences between children in terms of behavior and attitudes in context. It is also interesting to note that most of the differences relate to the same semantic dimension (e.g.: "John is more extroverted, while Michael is more timid") along which the twins take opposite positions. Therefore, the mutual positioning between the self and the other that leads to differentiate each other along dimensions made relevant and salient by all family members, assumes a crucial role in the construction of the personality. The therapeutic implications of these results will be discussed