Father of 63, and counting: meet the modern sperm donor

Houben has been donating sperm for more than 10 years now, first at the local sperm bank and then, after reaching the clinic's legal limit, privately via the internet. Most of his donating is done in his neat, modest flat on an estate on the outskirts of the Dutch town. The T-shirt he's wearing, which declares "Anytime, anyplace, anywhere, anyway", is actually a bit misleading. "In the old days I would gladly travel, and my colleagues covered for me if I was late to work," he says. "But my job at Maastricht's tourism office has changed and I have to be around much more. Now I ask people to come to me."

And they do, from all over the world. Houben has biological offspring in Australia, Israel, Canada, Cyprus, Germany and Luxembourg, as well as at home in the Netherlands. His current tally of donor-conceived children stands at an eye-watering 62, with the 63rd on the way. It is by no means a world record – Houben once watched an episode of Oprah about a man who has fathered 200, a number he says he'll never catch. But he has been called Europe's most prolific sperm donor, and he's happy to accept the title until someone has the, well, balls to challenge him.

In his late thirties, Houben is on what you'd term the cuddly side, and he'd be the first to deprecate his looks, although the digital photo frame that's scrolling through his brood – some fair, some dark, some hairless, puckered babies – reveals an unexpectedly attractive crop of kids. He's genial, bright and witty on the subject of his pastime; but what his recipients value most of all is his commitment.