They’re The Rarest Dicephalus Twins In The World
Dicephalus twins are a rare form of twin where two heads sit alongside one another on a shared torso. Dicephalus literally means “two-headed.” In most cases, the second head isn’t fully formed or one or both of the babies is born stillborn, making Brittany and Abby extremely rare.
Dicephalic twins make up only eleven percent of all the conjoined twins in the world. There are only three reported cases of dicephalic twins surviving into adulthood. Brittany and Abby are the only ones to have ever survived in the United States. There are two other cases, one in Italy and one in Turkey.