THE HAGUE — A Dutch fertility doctor who used his own sperm to father 49 children, without telling their mothers he was the donor, may have even more children.
The case of Dr. Jan Karbaat, who died in 2017, has riveted the Netherlands, due to its mix of unethical medical behavior, privacy concerns, DNA testing, legal wrangling, and the rights of children to know who their parents are.
Ties van der Meer of the Dutch Donor Child Foundation said Monday three more people contacted him during the weekend because they suspect they may also have been conceived using Karbaat’s sperm.
DNA tests revealed last week that Karbaat was the biological father of 49 children. Most of them are now adults.
Publicity surrounding the case means that the extended family may grow even larger as more people seek to check their DNA against Karbaat’s.
Van der Meer, whose foundation supports such children, said Karbaat could have fathered many more, including ones who are not in the country.
In the past, fertility doctors would advise parents not to tell their children they were conceived with the help of donors, he said.
Meanwhile, dozens of people who now know who their biological father is are coming to terms with the news.
‘‘We are all happy with the clarity and the information we now have so we can get on with our lives,’’ said Joey Hoofdman, one of the people fathered by Karbaat.
‘‘It is a wave of emotions. We are all happy we have met each other, but because there are so many, it is complicated,’’ he added.
Hoofdman said he will now seek compensation. He said his mother went to the clinic for a fertility treatment with the sperm of her partner, the man who raised Hoofdman as his son.
Karbaat’s fertility clinic in the town of Barendrecht, a suburb of Rotterdam, was ordered closed in 2009 by a government health care agency due to poor administration and record keeping. A phone number and e-mail address listed online for the clinic did not work.
The doctor died shortly before a legal battle began two years ago to check whether he was indeed the biological father of children born after their parents underwent treatment at his clinic.
Until 2004, people in the Netherlands who donated sperm or eggs could do so anonymously.
Van der Meer said Karbaat appears to have been able to father so many children in part because of the culture of silence that prevailed around sperm and egg donations in the 1970s and ’80s.
‘‘If something is kept secret from all sides, then the only person with all the information — and that is the doctor — has totally free rein,’’ he said.
In the legal battle, the doctor’s family had said its privacy was being called into question, but a lawyer for the children said the court ruling placed the children’s rights first over the privacy rights of Karbaat’s family.
The Dutch branch of child rights group Defense for Children, which supported the legal battle, welcomed the clarity and said it should be a first step toward allowing all children of anonymous donors to seek out their heritage.
‘‘The Karbaat case is the first enormous breakthrough,’’ said Iara de Witte, an adviser to the rights group.