Ed Houben, who was until recently single but has now started a long-distance relationship, has never taken any payment for his services, reports the Daily Telegraph.
He first volunteered his services through an IVF clinic but had to stop a few years ago because he had reached his quota of 25 donations.
Now people find him on the internet and through word-of-mouth. Families he has helped vouch for him by telling of their own good experiences.
Mr Houben has travelled to hotels across Europe to perform his duties as a sperm donor, which is done by self-insemination by the mothers.
"I receive expenses and still travel to meet couples sometimes when it suits them," he said. "But generally people come here to see me."
Because each child will grow up knowing Mr Houben is their biological father, there is no danger of any of his offspring ever meeting and having a relationship.
A group of families including 12 of his children recently attended a reunion at Mr Houben's home.
"The kids had the chance to play with their half-brothers and sisters, which was nice," said Mr Houben. "The families also got to know each other.
"Some of them introduced me to the kids and said this is your real dad. But to be honest it didn't mean much to the children. They just looked at me and smiled and then carried on playing." (Daily Telegraph)