It is possible for a set of twins to have two different fathers. The condition is called heteropaternal superfecundation, and it happens when a woman ovulates twice in one month and has sex with two different men while ovulating. There are only a few recorded cases of it in history (a lot of that could stem from the fact that DNA tests have only been around since 1984), but what is really amazing is that it has happened not once, but twice at the place where people go to get paternity matters dealt with.
The first case of two different men fathering a set of twins happened in 2008. A woman named Regina was on the show to see if her ex-boyfriend was the father of her twins, and he was only the father to one of them.
The second time was in 2011 when 19-year-old Alejandrina went on the show claiming that her boyfriend Jose was the father of her twins. She also emphatically denied sleeping with anyone else but Jose. Well, the lie detector determined that was a lie, and the DNA test proved that Jose was only the father to one of the twins.
Siblings can have different fathers – technically making them half-siblings – but what about twins? Yes, it can happen. In fact, one study estimates that as many as 1 in 400 sets of fraternal twins is “bipaternal.
Both times it happened on the show, Maury and the audience were shocked. Mostly by the whole “twins by different parents” thing, but probably at least in part by the fact that Maury is still on the air.