Results of DNA tests conducted this morning at a hospital in the southeaster city of Nijmegen "showed that 49 children in the case are direct descendants of the late Karbaat", the organisation said in a statement.
A fertility clinic doctor in the Netherlands fathered 49 children, after using his own sperm rather than that of donors.
Jan Karbaat, who died in 2017, has always been suspected of using his own semen at his now closed Rotterdam fertility clinic without the knowledge of the women.
The doctor had always denied the accusations, but it was revealed on Friday after DNA tests were made public by a Dutch court.More news: Chelsea ace Hazard: We MUST qualify for Champions League
A Dutch fertility doctor used his own sperm to illegally father at least 49 children, DNA test results have revealed.
Before he passed away, it has been claimed that Karbaat admitted to fathering around 60 children in his time at the clinic which closed in 2009 following reports of irregularities.
He said he had sometimes mixed his sperm with that of other donors.
In 2017, he was taken to court by a group of donor children and their parents.More news: Disney+ Confirms Vision and Scarlet Witch, What If?, And More Marvel Shows
The Karbaat family's lawyers had argued that their clients' right to privacy had to be respected.
Martijn van Halen, one of the doctor's children, told Dutch news website nrc.nl: "It's nice to know for sure".
"After years of uncertainty, the plaintiffs are finally closing a period and they can start processing the fact that they are one of [his] many descendants".
Many of the Karbaatkinderen have become friends after their two-year-legal fight and Mr van Halen said would be keeping in touch with some of his half siblings.More news: Pope Francis kisses shoes of Sudanese leaders in plea for peace
Applicants can apply in writing to an official body called the FIOM, which maintains a DNA database to match children conceived via anonymous donors.