Talk about hard to explain. One mother in Vietnam had her twins genetically tested and found out the children were fathered by two different men. After being constantly prodded by family members inquiring about the twins’ vastly different appearances, the 2-year-olds underwent a paternity test, to shocking results. While the two shared a mother, they were bipaternal, meaning the twins were fathered by two different men within the same ovulation cycle.
Suspicion from family members arose because of the twins' unrelated appearances. Although they were fraternal twins (not identical), their lack of similarities were well noticed. As the two grew up, one had very thin, straight hair, while the other had lush, wavy hair. The family's concern prompted the 34-year-old father (well, one of them) and mother to bring the twins to the Center for Genetic Analysis and Technologies in Hanoi, Vietnam — where they found the twins to be half siblings.
Fraternal twins are born when a woman releases two eggs during ovulation, leading to two separate instances of fertilization. This often happens through one act of intercourse but can also occur through two instances of intercourse within the same week of ovulation — and in some cases, with more than one partner.
Superfecundation, the fathering of twins by two separate men, is an incredibly rare event, but perhaps not as rare as you might suspect. A similar case was found in the U.S. last year when a New Jersey judge ruled two different fathers to one set of twins to pay child support for the children who were fathered within the same week.
According to statistics from the National Institute of Health, as many as one in 12 sets of fraternal twins are caused by superfecundation (although that often means the same father of both children). In the US, an estimated one in 400 sets of fraternal twins born to white women are bipaternal. It's also estimated that about 2.4 of paternity suits involving fraternal twins includes an occurence where the fathers are different.
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Editor's note: This article has been updated to reflect accurate statistics.
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