From uncanny coincidences to shared biology, we asked the experts to explain the real forces behind the phenomenon.

Mirror Twin: They are literal mirror of each other, with opposite hair whorls, birthmarks, and even dominant hands. This happens when an egg splits later than usual, around 7 to 12 days post ...

Thirteen days before the start of the Second World War, a 35-year-old unmarried immigrant woman gave birth slightly prematurely to identical twins at the Memorial Hospital in Piqua, Ohio and ...