Children born with the help of Karbaat's clinics celebrate after the court ruling.
CNN  — 

A fertility doctor suspected to have fathered scores of people by secretly swapping donors’ sperm for his own will have his DNA tested, after a Dutch court supported a legal challenge by 22 of his potential children.

The group were all conceived with the help of fertility doctor Jan Karbaat, who died in 2017 at the age of 89 and had long been suspected of using his own sperm to impregnate clients – a charge he denied.

But a court ruled Wednesday that Karbaat’s family must allow his DNA to be examined, after agreeing that there was sufficient evidence that he did use his own sperm.

DNA from Karbaat’s son, who is still alive, has already been found to hold a “relevant biological relationship” with 47 people the doctor helped conceive, and a documentary that aired in the Netherlands suggested Karbaat may have fathered up to 200 children.

The court also agreed that it is “undisputed that a number of donor children have similarities in appearance” to Karbaat.

Karbaat’s DNA has already been recovered, after a court backed a similar challenge in 2017 – but it has remained in a safe since then, and the claimants had not previously been allowed to access it, because the judge did not feel enough evidence existed at that time to allow for it to be compared.

Karbaat worked as a fertility doctor for decades, first in hospitals, then at a clinic in Rotterdam and later at his own clinic in the same city.

When his clinic shut down in 2009, a significant number of “abuses with donor seeds and administrative abuses” were discovered, including exceeding the agreed number of children per donor.

CNN has contacted Karbaat’s family for comment.