A Dutch sperm donor is reported to have fathered 102 children after donating at 11 different clinics.
The authorities in the Netherlands have launched an investigation into the man whose identity has not been disclosed.
Under Dutch law sperm donors can father no more than 25 children. This is intended to minimise the risk of children later entering into a relationship with a half sibling.
Donors are required to enter into contracts pledging not to donate at different clinics, but this provision if frequently unenforced.
RTL reported that it had identified a second man who has donated sperm at more than one clinic.