For two sisters raised in a family of 11 children that moved back and forth between Washington state and South Dakota, danger didn’t come from outsiders like they’d been warned by their church.

It came from their brothers in the next bedroom.

Lynn said she was still in diapers when her abuse began. Two older sisters told her how they caught one of their brothers touching her. The sisters told their mother, but Lynn said her parents did nothing; the abuse continued until he was 16 and she was 10. Years later, Lynn’s sisters offered a devastating explanation for their brother’s behavior: They believed he had been sexually abused, though by a neighbor.

Katherine, the family’s second-youngest child, said she was about 2 when it started for her. She was abused by a different brother. He, too, had been abused by an older cousin, she said in an interview.

Before long, the two sisters started to repeat the pattern. When she was 10, Lynn said, she took her younger brother out behind a shed and pulled his pants down. She’s blocked the memory of what she did next, but she remembers him running away. Katherine has a similar memory: She was 5 when she said she abused a nephew, who was 3 or 4.