DNA tests have proven that a Dutch fertility doctor used his own sperm to secretly father 49 children.

Jan Karbaat, who died two years ago in April 2017, impregnated the women at his clinic in Bijdorp, near Rotterdam in the Netherlands, with none of the women aware that he was illegally using his own semen in the operations.

However, it is feared that he could have fathered many more children than the 49 identified.

The court case began in 2017 when 22 children applied for legal help in resolving their true heritage after suspicions grew they could be related. Many of them bore close physical resemblances and had highlighted irregularities between their appearances and the appearances of their alleged donors.

The doctor is said to have told a donor child in 2011 that he used his own sperm to inseminate women, but always denied the claims, with the legal case against him starting shortly before he died aged 89.

When he was alive, a judge felt there was insufficient evidence to allow the test and when he passed away, his family fought against the use of his DNA, which was allegedly extracted from personal items including his toothbrush.

However, following a two-year legal battle from dozens of his children and their parents, a court ruled in February that his DNA could be released.

Results released on Friday proved that Karbaat was the father of the 49 children, said the group Defence for Children which had supported the case.

"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."

Martijn van Halen, one of Mr Karbaat's children, told Dutch news website nrc.nl that he felt good about finally getting the truth, stating: "It's nice to know for sure. It gives peace."

Another of the children named Joey, said he could "finally close the chapter" now he knew Karbaat was his father.

"After a search of 11 years I can continue my life. I am glad that I finally have clarity," he told Dutch broadcaster NOS.

Many of the children, most of whom are now in their 30s, have become friends after their lengthy legal bid and claimed they would be keeping in touch.

Tim Bueters, a lawyer who represented the children, claimed he was pleased to have results of the case after years of uncertainty.

"It means that there is finally clarity for the children who are matched," he told NOS.

Karbaat's clinic was closed in 2009, amid allegations of false data, and methodical exceeding of the permitted number of six children per donor.

DNA tests have proven that a Dutch fertility doctor used his own sperm to secretly father 49 children.

Jan Karbaat, who died two years ago in April 2017, impregnated the women at his clinic in Bijdorp, near Rotterdam in the Netherlands, with none of the women aware that he was illegally using his own semen in the operations.

However, it is feared that he could have fathered many more children than the 49 identified.

The court case began in 2017 when 22 children applied for legal help in resolving their true heritage after suspicions grew they could be related. Many of them bore close physical resemblances and had highlighted irregularities between their appearances and the appearances of their alleged donors.

The doctor is said to have told a donor child in 2011 that he used his own sperm to inseminate women, but always denied the claims, with the legal case against him starting shortly before he died aged 89.

When he was alive, a judge felt there was insufficient evidence to allow the test and when he passed away, his family fought against the use of his DNA, which was allegedly extracted from personal items including his toothbrush.

However, following a two-year legal battle from dozens of his children and their parents, a court ruled in February that his DNA could be released.

Results released on Friday proved that Karbaat was the father of the 49 children, said the group Defence for Children which had supported the case.

"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."

Martijn van Halen, one of Mr Karbaat's children, told Dutch news website nrc.nl that he felt good about finally getting the truth, stating: "It's nice to know for sure. It gives peace."

Another of the children named Joey, said he could "finally close the chapter" now he knew Karbaat was his father.

"After a search of 11 years I can continue my life. I am glad that I finally have clarity," he told Dutch broadcaster NOS.

Many of the children, most of whom are now in their 30s, have become friends after their lengthy legal bid and claimed they would be keeping in touch.

Tim Bueters, a lawyer who represented the children, claimed he was pleased to have results of the case after years of uncertainty.

"It means that there is finally clarity for the children who are matched," he told NOS.

Karbaat's clinic was closed in 2009, amid allegations of false data, and methodical exceeding of the permitted number of six children per donor.