This "fascinating" account of two sets of identical twins separated at birth offers "a unique window into human behavior and development" (Steven Pinker, New York Times–bestselling author of The Blank Slate).

Accidental Brothers tells the extraordinary story of two sets of identical Colombian twin brothers who discovered at age twenty-five that they were mistakenly raised as fraternal twins—when they were not even biological brothers. Due to an oversight that presumably occurred in the hospital nursery, one twin in each pair was switched with a twin in the other pair. The result was two sets of unrelated "fraternal" twins—Jorge and Carlos, who were raised in the lively city of Bogotá; and William and Wilber, who were raised in the remote rural village of La Paz, 150 miles away. Their parents and siblings were aware of the enormous physical and behavioral differences between the members of each set, but never doubted that the two belonged in their biological families.

Everyone's life unraveled when one of the twins—William—was mistaken by a young woman for his real identical twin, Jorge. Her "discovery" led to the truth—that the alleged twins were not twins at all, but rather unrelated individuals who ended up with the wrong families.

Blending great science and human interest, Accidental Brothers will inform and entertain anyone interested in how twin studies illuminate the origins of human behavior.

"Fascinating . . . Segal presents intriguing data regarding twins and the effects of nature and nurture." —Susan Stump, Multiples of America

"Thorough . . . Essential for psychology students; fascinating for lay readers." — Library Journal, starred review

"Utterly fascinating and comprehensive." — Booklist

"A compellingly readable tale of identity formation." — Kirkus Reviews