Speaking to the MailOnline, Defence for Children - an organisation representing parents and children born through his now-closed clinic - said: "The results confirm serious suspicions that Karbaat used his own sperm at his clinic".
The Dutch doctor, now deceased, allegedly used his own sperm instead of those from a donor to inseminate patients.
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 tests revealed Dr Karbaat had impregnated the women at his clinic near Rotterdam and the results were confirmed earlier this year after Rotterdam District Court allowed their release.
Jan Karbaat was first taken to court by a group of donor children and their parents in 2017 over suspicions they were related.
LEGO Star Wars 75244 Tantive IV officially announced
The next LEGO Star Wars exclusive set will be 75244 Tantive IV from the opening of the original 1977 movie. The radar dish, for example, also functions as a handle to make the ship a little easier to transport.
The Karbaat family's lawyers had argued that their clients' right to privacy had to be respected.
Tests carried out subsequently proved Dr Karbaat was the father of the 49 children - although it is now thought he may have fathered even more children.
"Sperm belonging to the late doctor was also distributed to other clinics", the organization said.
"Now, after years of uncertainty the plaintiffs can finally close a chapter and start processing the fact that they are one of Karbaat's many descendants", De Witte said.
Martijn van Halen, one of Mr Karbaat's children, told Dutch news website nrc.nl: "It's nice to know for sure".
One mother was particularly suspicious given her child's striking resemblance to the doctor.