Twin concentration-camp survivors Stepa Heller, left, and Annetta Able, with their birthday cake in 2019. The inmate number that Heller was given at Auschwitz can be seen tattooed on her arm. Courtesy of Daphna Able Nazis wanted identical twin Annetta Able to get pregnant by another identical twin at Auschwitz. Dr. Josef Mengele, known as the "Angel of Death," treated her and her sister as human guinea pigs. Able's horrific story features in a new book about twins who survived these Holocaust "experiments." Soon after Annetta Able and her identical twin sister, Stephanie Heller, were liberated from Auschwitz, they learned...