About 600 people might be able to call Bertold Wiesner "Dad."
The British biologist who operated a fertility clinic since the 1940s may have fathered between 300 and 600 children, the Telegraph reports. Until recently, it was unknown Wiesner had been making most of the sperm donations at the clinic that has helped nearly 1,500 families conceive children.
But two men who were conceived at the center have recently come forward with research and DNA tests that suggest Weisner fathered a multitude of offspring.
Today, laws in the United Kingdom prohibit men from making bulk donations, in order to eliminate the possibility of two siblings meeting and procreating, according to the report.
But in the United States, some sperm banks have no set regulations to prohibit men from donating multiple times, according to a September report by ABC News.
One Washington mother discovered her son, who was conceived using sperm from a donor, had at least 150 half-siblings, The New York Times reports.
Kirk Maxey, a former sperm donor, estimates he's fathered about 200 to 400 children with his donations.
Now a doctor, Maxey says he worries about his children inadvertently committing incest, and he's pushing for regulations that let parents and donors know the whereabouts of their possible children.
"I have a son that lives in the area and most of the patients came from a 100- or 150-mile radius of the area," he told ABC's Nightline in 2006. "If you do math, again, there may be 100 young women that are basically my son's age that are his half-siblings.
One California virgin who's fathered 14 children through sperm donations is facing a different battle, however.
A self-proclaimed "donorsexual," Trent Arsenault says he commits all of his sexual energy to providing sperm to families having trouble conceiving.
But the 36-year-old has faced backlash from the Food and Drug Administration, which has issued a cease-and-desist order on his donations," KTVU reports. The FDA argued Arsenault did not take the necessary precautions to prevent the transmission of certain diseases.
For more on biologist Bertold Wiesner's case, visit the Telegraph.