A Dutch fertility doctor used his own sperm to illegally father 49 children, DNA tests have shown.Jan Karbaat, who died two years ago, impregnated the women at a clinic near Rotterdam.The tests took place after a court agreed in February to release his DNA following a legal bid by dozens of his children and their parents.Results released on Friday proved that Mr Karbaat was the father of the 49 children, said the group Defence for Children which had supported the case.Most of the children are now in their thirties.Mr Karbaat used his own sperm to father the children instead of a chosen donor and the legal case against him began shortly before he died aged 89.The doctor's family fought against the release of his DNA, which Dutch media said was extracted from items such as a toothbrush locked in a safe."The judge placed the interest of the child above the right to privacy of Mr Karbaat and his family," said Defence for Children adviser Iara de Witte."After years of uncertainty, the plaintiffs are finally closing a period and they can start processing the fact that they are one of the many descendants of Karbaat."The clinic where the doctor worked closed down in 2009, but groups representing the so-called "Karbaatkinderen" believe Mr Karbaat may have fathered many more children than the 49 identified.Martijn van Halen, one of Mr Karbaat's children, told Dutch news website nrc.nl: "It's nice to know for sure.

It gives peace."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.