The oldest child is nine and the youngest two months old.
Houben is now far removed from his previous life as a 34-year-old virgin still living with his mother.
He runs his baby-making business for free, when sperm banks generally charge thousands of dollars for artificial insemination, the Mail said.
The business sees women come to him from across the world or he can go to them if they cover his travel expenses and accommodation.
Since the launch of his business he's been getting lucky - he says he sleeps with around 15 childless women a month in a bid to make their quest to become mothers a reality.
With a no strings attached policy, he asks his partners to sign documents waiving any legal claim to child support.
"My girlfriend says that what I do only makes me more interesting," he told Germany's Der Spiegel magazine.
"She's coming to visit again soon but she hasn't managed to get pregnant yet," he said.
Houben is understood to be the most prolific professional baby-maker in the world.
His success rate is high - 80 per cent of the women he sleeps with fall pregnant.
The website Spermaspender.de in Germany is one the websites he uses to connect with childless women desperate to conceive.
All his partners must submit medical records showing they are disease and drug-free.
Included in his paper work is a semen analysis known as a 'spermiogram' which shows he is the real deal - a sperm count of less than 20 million shows the potential donor is "not a good prospect."
Prospects are increased for sperm counts of 80 to 100 million.
Houben's count is 100 million. "I don't fire blanks," he joked.
