(CNN) - Investigators say a fertility clinic doctor in England may have fathered as many as 600 children. The London Telegraph reports doctor Bertold Wiesner apparently used his own sperm hundreds of times to fertilize eggs for patients. He started a clinic in the 1940s.
Two men who learned they were the doctor's biological sons made the discovery after years of research. DNA tests conducted on 18 people conceived at the clinic found two-thirds of them were fathered by Wiesner. Wiesner died in 1972 and most of his medical records were destroyed.