How Can Twins Have Two Different Fathers?


A woman in New Jersey only discovered that her twins have different fathers after she had DNA testing done to establish paternity when the children were 20 months old. This is not a photo of the twins in question. (Photo: Getty Images).

One New Jersey woman got the surprise of a lifetime when she discovered that her 2-year-old twins have two different fathers.

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The mother (identified as “T.M.” in court documents) got the news this winter, when she received the results of a paternity test mandated by family court as part of her application for public assistance, The New Jersey Law Journal reported on Thursday. The Passaic County Board of Social Services had required the mother to establish paternity of the twins — in order to make the toddlers’ father pay child support — because she revealed that she’d been intimate with another man during the same week in which she believed her children were conceived with her former partner. DNA test results revealed in November that T.M.’s partner was the father of only one of her children.

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Karl-Hans Wurzinger, the laboratory director of the Identity Testing Division at Laboratory Corporation of America where the DNA was tested, reportedly testified at the subsequent child-support hearing that, “The twins born to T.M. were born from two eggs that were fertilized from different fathers during the same menstrual cycle.”

According to Passaic County Superior Court judge Sohail Mohammed’s ruling, “An article Wurzinger published in 1997 said approximately one in every 13,000 reported paternity cases involved twins with separate fathers,” reports the New Jersey Law Journal. (Wurzinger declined Yahoo Parenting’s request to comment on the case). 

The phenomenon, known as “heteropaternal superfecundation” is so rare, a rep for the American College of Obstetricians and Gynecologists confirms to Yahoo Parenting that they don’t even have statistics on it, though a couple of instances have been chronicled in years past on the talk show Maury, previously called the The Maury Povich Show.

“This is definitely one of those, ‘Wow,” stories,” Shari Brasner, an obstetrician at Mount Sinai Medical Center in New York City, tells Yahoo Parenting. But it may occur more often than we realize, she adds, because “paternity isn’t always contested so there are probably scenarios in which this has happened but nobody knows. You don’t blink an eye at fraternal twins looking different after all.”

How it happens isn’t all that complicated actually. “Twins in general, especially fraternal twins, result from two different eggs being fertilized by two different sperm,” says Brasner. “But ovulation doesn’t necessarily happen in the same moment.” Sperm is viable for up to five days, says Brasner, so if a woman has sex with a man, ovulates, then has sex with another man within that five-day window, it could result in twins from two different men. “It’s not the most common thing I see in my practice,” she adds. “But I could see scenarios where that happens. It’s definitely possible.”

And with the use of reproductive technology on the rise, it may happen more often in years to come. “Fertility drugs are designed to stimulate ovaries to produce more than one egg in ovulation cycles,” says Brasner, noting that there are also instances in which another man’s sperm is deliberately added to the mix. “Combining donor and spouse sperm improves the chances of conceiving in general,” she says, “and that creates yet another scenario that could result in twins from two different men.”

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