Bertold Wiesner and his wife Mary Barton founded a fertility clinic in London in the 1940s and helped women conceive 1,500 babies.
It was thought that the clinic used a small number of highly intelligent friends as sperm donors but it has now emerged that around 600 of the babies were conceived using sperm from Mr Wiesner himself.
Two men conceived at the clinic, Barry Stevens a film-maker from Canada and David Gollancz, a barrister in London, have researched the centre and DNA tests suggest Mr Wiesner, an Austrian biologist, provided two thirds of the donated sperm.
Such a practice is outlawed now but at the time it was not known that Mr Wiesner was providing the majority of the samples.
The same sperm donor should not be used to create so many children because of the risk that two of the offpsring will unwittingly meet and start a family of their own, which could cause serious genetic problems in their children.
Image: Lab pipette, via Shutterstock.