GROWING up, Martijn van Halen couldn’t help but notice the stark differences between him and his father – so it came as little surprise to him when he was told he was conceived via a donor.
But then things took an unexpected turn when he discovered the shocking truth about his conception.
The donor had in fact been a Dutch fertility doctor who had secretly used his own sperm to impregnate unsuspecting women.
And Martijn, 44, reveals he has more than a hundred half-siblings in a WhatsApp group he set up – and suspects there could be dozens more.
Speaking exclusively to The Sun, he says: “In my group we have 102 people who have all matched to his DNA.
“We can only know for sure if they test their DNA. There are still a lot of people who don’t even know they were donor conceived.
READ MORE REAL LIFE STORIES
“There’s a new DNA match every month. In another few years, it will be 250, that’s what I expect.”
The dad-of-two is speaking out ahead of new BBC documentary series Seeds of Deceit about the doctor, Jan Karbaat, who deceived countless women at his IVF clinic near Rotterdam in the Netherlands.
Karbaat, who died in 2017 aged 89, was a pioneer in the field of artificial insemination from the 1980s to the 2000s.
His family fought against the release of his DNA, but following a lengthy legal bid by dozens of his children, including Martijn, and their parents, Rotterdam District Court overruled the privacy objections of Karbaat’s widow in 2019.
A judge ordered the profile to be made available to those that may be linked to Karbaat.
It is believed he helped produce 10,000 children during his three decades at his sperm bank – so Martijn’s prediction could be an underestimation.
He could potentially have thousands of half-siblings.
Only recently Martijn, who owns a garden centre in the Netherlands but now lives in Luxemburg with his second wife Kim, 43, says he was contacted by a 16-year-old girl after her DNA had matched to his.
He says: “She couldn’t understand how she had so many uncles and aunts.
“Her mum didn’t know anything about it. She found out she was a donor child through her daughter doing a DNA test. That was quite a shock.”
‘Spider’s web’ family tree
Comparing his family tree to “a spider’s web”, he says he was very open with Kim when they first met about his origins due to the possibility of unknowingly having relationships with half-siblings.
And he has also explained it to daughters – Frederique, 14, and 10-year-old Carlijn – from his first marriage so they are aware.
Martijn says: “The chances of this are really great. My children still have to be really careful.”
He adds: “It’s been an interesting story to share.”
His parents went to the clinic in the town of Barendrecht, which closed down in 2009 after irregularities were detected in its record-keeping, after being unable to start a family.
Martijn’s younger brother was also conceived there, and they were assured the same donor would be used for both, but DNA tests have since revealed they are half-brothers.
Former landscape gardener Martijn only learnt of his origins 10 years ago, when the man who had raised him – and who he thought was his father – told him he was a donor child.
The chances of this are really great. My children still have to be really careful
Martijn van Halen
Martijn says: “My parents always planned to tell me and my brother when I turned 18, but when I was 16, my mother died in a traffic accident.
“We’d just lost a parent and so he didn’t tell us and life went on.”
It came to light after one of Martijn’s nephew’s was diagnosed with an inherited disability.
He says: “The doctors were asking, ‘Are there any problems in your family?’ Dad changed his mind. It was very difficult for him.
“For us it was like a puzzle came together. I had always noticed something but didn’t know what.
“I don’t look anything like him and we have very different viewpoints.”
Before finding out about Karbaat he had already found out he had 25 half-siblings after checking a DNA database.
On learning that Karbaat was his biological father, he recalls: “My parents were lied to but for me, it wasn’t that bad.
“It was not a good thing, of course. He did things that were not allowed. It was unethical. It was 40 years ago, the medical world was very different.
“I always look on the bright side, to quote Monty Python. I’m lucky I’ve got strong genes.”
I always look on the bright side, to quote Monty Python. I’m lucky I’ve got strong genes
Martijn van Halen
He says the similarities between him and his half-siblings are striking “not only on appearance but on interests”.
Martijn says: “From the chin to the forehead, we’ve all got a lot of similarities. We find it really easy to learn and find good jobs.
“My half siblings are all doctors or on the board of good companies, or entrepreneurs.”
He adds “strange things happen” all the time: “While my half-sister Moniek was doing her PhD, her professor put her together with another student as he thought they would be a great match to do their research together.
“Then, two years ago, this other woman did a DNA test and found out that she was one of us. That’s so strange.”
Martijn is in regular contact with his half-siblings and his WhatsApp group is very active.
He says: “It’s just a bit of chat but also serious things like supporting someone if they are going through something like a divorce.”
He plans to meet up with some of them when he returns to the Netherlands this week and says “a few have been on holiday to my campsite” in the South of France, that he runs with Kim.
He broke the news to his daughters a few years ago.
He says: “They might have seen some news or information online. They said, ‘Oh we’ve got lots of cousins, that’s nice’.”
Martijn says they will never know Karbaat’s motives for such a large-scale deception.
“We can’t ask him, of course, because he’s dead. We, as a group, have several theories we have put together,” he explains.
We can’t ask him, of course, because he’s dead. We, as a group, have several theories we have put together
Martijn van Halen
“At the time the product had to be fresh because the technique of using frozen sperm was not available.
“If a donor didn’t turn up and he had a woman at the clinic desperately wanting a child, at first it was out of necessity, because he could not help his patients.
“But then perhaps it was a little bit of an ego thing and the financial part. It was big business.”
Asked how he feels towards his biological father, he adds: “I have got my father who raised me.
“I have got 50 per cent of my genes from Karbaat, but he is not my father.”
All episodes of Seeds of Deceit are streaming from Monday December 4 on BBC iPlayer.