A man who has fathered between 550 and 600 children over the past 16 years is not allowed to donate any more sperm to prospective parents, a court in the Netherlands ruled on Friday.

According to The Hague District Court, the man lied about the number of children he had already fathered, the number of sperm donations he had made and his intention to donate even more sperm.

“All these parents are now confronted with the fact that the children in their family are part of a huge kinship network, with hundreds of half siblings, which they did not choose,” the court said.

Because of Dutch privacy laws, the government has not publicly named the man, Jonathan Jacob Meijer, 41, in the court proceedings as the donor in question. However, in an email to The New York Times for a 2021 article about him, a spokesman for the health ministry confirmed his identity. “Donors must sign an agreement with their clinic that they don’t donate sperm at other clinics,” Gerrit-Jan KleinJan wrote. “The sperm donor you are writing about made this agreement as well. Nevertheless, he donated at more sperm banks resulting in 102 babies.”

The court’s ruling came after Mr. Meijer was sued by the Dutch Donor Child Foundation, which represents the interests of sperm donors’ children, and a mother who had one of his children. “The children deserve a rest,” the mother, who went by Eva but omitted her last name, said in a statement on Friday.

Citing negative psychological consequences for the children, the court said that barring Mr. Meijer from continuing to donate was in the children’s best interest. It would be hard for them to cultivate relationships with so many biological half siblings, and it adds to a higher chance of incest, the court said.

In the Netherlands, Mr. Meijer donated sperm to at least 11 fertility clinics, according to court documents. Each of those clinics allows his sperm to produce 25 children or be donated to a maximum of 12 mothers, as is the rule in the Netherlands. Mr. Meijer also lied to the clinics, according to court records, telling each clinic that he hadn’t donated elsewhere and wasn’t planning on doing so in the future.

A report from 2017 concluded that Mr. Meijer had fathered 102 children through Dutch clinics between 2007 and 2017. Between 2015 and 2018, he also donated sperm to a fertility clinic in Denmark that, at the time, didn’t place a limit on the number of children produced from donated sperm and that sent semen to people in other countries.

In addition to his clinic donations, Mr. Meijer also offered his sperm on various social media platforms in the Netherlands and abroad. According to the court, Mr. Meijer keeps in touch with multiple parents.

The Dutch Donor Child Foundation — which posted an image of two clinking champagne glasses on Twitter in celebration of the verdict with the words “important step forward!” — supported the ruling. “We’re happy that the judge ruled that it’s not a good idea to have countless half-siblings,” Ester de Lau, a board member, said.

Dutch lawmakers are in the process of implementing new rules for sperm donors to protect the interests of the children. The Dutch House of Representatives debated the issue this month.

“In the Netherlands, we think it’s important that everyone has facts about their lineage,” according to Ernst Kuipers, the minister of health, welfare and sport. It has been possible for donor children to request such information since 2004. But the government wants to establish a central registry that would show whether a sperm donor has donated to multiple clinics.

“The new rules would discourage undesirable situations in which sperm donors sometimes father hundreds of children,” according to the proposed bill.

Ms. de Lau said she supported the bill, but that it needed to go further to ensure that donor children could also look up any possible private donations and donations abroad. “The registry can start in the Netherlands, but needs to be international,” she said. “This isn’t something that is limited to the Netherlands.”

Rules surrounding sperm donation vary across Europe. In Belgium, the health minister announced a similar registry after it became clear that Mr. Meijer had also been active there.

Richard van der Zwan, Mr. Meijer’s lawyer, told the court that his client wanted to help parents who had trouble conceiving, The Associated Press reported. Mr. van der Zwan couldn’t immediately be reached for comment on Friday.

Mr. Meijer said he was not acting selfishly and that his continued sperm donations would not negatively affect any subsequent children, the court said. But the court ruled that the interests of the children and other parents outweighed those of Mr. Meijer’s to continue to offer himself as a donor.