More: It took three babies until I was finally able to breastfeed
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.
More: Why I don't care if you think I'm a bad parent
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.
More: I found out the hard way that the perfect mom doesn't exist
According to the National Institute of Health, approximately 1 out of every 12 sets of fraternal twins is fathered by two different men. That's about 1 in every 13,000 births, which is a whole lot of mamas with some serious explaining to do.