A tribute to the life and career of Dr Milton Diamond, a leading figure in twin studies of transsexuality and gender identity, is presented. Dr Diamond is famous for revealing the truth about the unsuccessful effort to change a monozygotic male Canadian twin into a female, following accidental ablation of his penis during circumcision. A short summary of recent twin research on human sexuality and transsexuality, focused on Dr Diamond’s contributions, is then presented. The tribute and overview are followed by research reviews involving the loss of a twin brother; oxytocin adminstration during twin delivery; models of monochorionic twinning; and twins’ brain responses to watching films. The final section of this article covers topics of human interest, including the passing of the world’s oldest conjoined twins; twins discordant for child abuse; twins married to twins; the delivery of a rare quadruplet set; questions of coincidence; and reared-apart twin valedictorians.

A review of an unusual twin type—twins born to women with two uteri (uterus didelphys)—is presented. This review is followed by summaries of recent research and perspectives concerning prenatal aneuploidy screening for twin pregnancies, twin conceptions by same-sex male couples, legal personality of conjoined twins, and a twin study of cannabis use. Interesting information about twins that has appeared in the media is also presented, namely how being taken for twins saved a pair of sisters; twin children of a jailed Nobel Prize winner, British ‘biracial’ twins, triplets born at the start of Russia’s attack on Ukraine, and twins born in different years.