Twins reared apart: a forgotten case/twin research reviews: X-inactivation and female co-twin discordance for hemophilia; transplantation for breast reconstruction; chimerism and telomere attrition in dizygotic twins; divergent life histories in twins reared apart/current concerns: high ACT-scoring twins; dating a twin; when gender identities diverge/the Holland twins.

A forgotten story of monozygotic twins reared apart is described. The pair, born in 1941 in Fribourg, Switzerland, were separated due to switch-baby incident in the hospital. This caused one twin to be raised as a singleton by an unrelated family, and the other twin to be raised as a 'dizygotic' twin with an unrelated child. This is followed by reviews of recent twin research and case studies of X-inactivation and hemophilia, breast reconstruction, chimerism and life histories. The final section of the article includes human interest pieces on academic twins, dating twins, transsexual twins and athletic twins.