Although she has two half-sisters from her dad’s previous marriage, there was nothing in Jess Pearce’s childhood to make her doubt her biological origins. She tanned, her father tanned; he was tall, so was she. Yet when she was 28, her mother dropped a bombshell.
“She sat me down one Sunday afternoon and said she had something she wanted to tell me,” Jess recalls. “She looked quite upset, and I thought, ‘She’s going to die.’” Instead, her mother told her, “Your dad isn’t your real dad.”
Jess’s father had undergone a vasectomy after his...