“…The key question is whether the presence or absence of the co-twin is problematic. Adverse effects of the inter-twin relationship on social and academic engagement, particularly problems associated with competition, dominance and identity development, have been presented as the justification of decisions to separate (Beauchamp and Brooks, 2003; Hay and Preedy, 2006; Segal and Russell, 1992). However, the assumption that the co-twin relationship may impede healthy social interaction and academic attainment has derived from the publication of small group analyses (Ballarà and Bollea, 1994; Paluszny and Gibson, 1974) and highly salient case studies of twins with problematic or pathological relationships (Luria and Yudovich, 1959; Wallace, 1996) rather than from larger community samples.…”