With each documentary and news report about Louis’ children, awareness of his story has grown. So have the Facebook and WhatsApp groups the siblings use to communicate. The web got more tangled still when one mother was angered to learn her donor was mixed race. She talked to a Belgian newspaper and, Joyce says, a neo-Nazi group threatened to “come for Louis”. Some siblings were against even an anonymous interview, partly out of concern for his safety: “But I think he should tell his story now,” Joyce says, “and not just be talked about.”

Louis is matter-of-fact about the ethics of his endeavour. He feels no remorse, but for some the experience has been fraught. Each child arrives with their own story – and questions. Ivo van Halen, 34, learned only recently that his parents had been preparing to tell him the truth about his parentage, until his mother died in a car crash. Ivo was 11, and his father lost the courage; he couldn’t risk losing his sons. They had his hair colour and never suspected he was not their father (Ivo’s brother is from another donor). But five years ago, Ivo’s father called his sons together and told them. “We said it changed nothing,” says Ivo, who works in IT. “I felt sad for him, that he’d had so much difficulty with it.”

Ivo felt little need to find his biological father until he, too, saw a documentary featuring some of Louis’ children. The story had now become part of a bigger scandal in Holland, after it was revealed that the doctor who ran one sperm bank Louis used had secretly donated his own sperm, and mixed it with other donations to increase the chances of conception (the doctor has since died). Watching it, Ivo says, “I thought, ‘Wow, these people even move like me. OK, now I want to know.’” He did a DNA test, and joined the Facebook group.