'20/20' REPORTS ON TWINS SECRETLY SEPARATED AT BIRTH, STUDIED FOR SCIENCE AND KEPT IN THE DARK ABOUT THE TRUTH UNTIL ADULTHOOD

Hour Searches for Answers as to Who Was Involved in the Shocking Experiment

'20/20: Secret Siblings' Airs Friday, March 9 (10:00-11:00 p.m. EST), on ABC

"20/20" features reunion of Howard Burack and Doug Rausch, twins who didn't know they were separated until they were adults.

An unknown number of Americans reached adulthood without knowing and experiencing a fundamental part of their identity - that they have an identical twin. "20/20" features the stories of three of these people who made this astounding discovery, a shocking truth that was deliberately kept secret from them most of their lives. These twins were separated as infants, given up for adoption to different parents and then monitored for a little known "nature vs. nurture" study - conducted completely in secret - by a preeminent psychiatrist. Anchor Elizabeth Vargas as well as filmmaker Lori Shinseki, director of the documentary "The Twinning Reaction," have been on relentless hunts for answers as to who was responsible for disrupting the lives of these twins and robbing them of their true identities. "20/20" tries to find out just how many twins and triplets were separated, interviews people involved in the study and shares a reunion of two twins, now adults. "20/20: Secret Siblings" airs Friday, March 9 (10:00-11:00 p.m. EST) on ABC.

Decades ago, a prominent New York City adoption agency separated at least five sets of twins and triplets, based on the recommendation of a psychiatrist, Dr. Viola Bernard. The agency never told the adoptive parents their child had an "other." Subsequently, under the guidance of another psychiatrist, Dr. Peter Neubauer, researchers tested, filmed and interviewed some of the children and families for years, under the pretense of conducting an "adoption study" without the knowledge or informed consent of the twins and their adoptive families.

"20/20" is anchored by Elizabeth Vargas and David Muir. David Sloan is senior executive producer.