How can this happen, you ask? Well apparently if a woman releases two eggs, and each one is fertilized by sperm from different sexual partners during the same ovulation cycle, so-called bi-parental twins can occur. It's kind of like getting pregnant on your period; it's so, so unlikely, but it's not impossible.
What happened in Vietnam is far more unusual than a period pregnancy, of course, as noted by Le Dinh Luong, president of the Genetic Association of Vietnam, who said, "This is rare not only for Vietnam, but for the world." The world.
A similar case was reported in 2009 to an American woman named Mia Washington who later admitted to having an affair when she conceived.
In this more recent case, DNA testing confirmed the Vietnamese twins have different fathers after one dad questioned the stark differences in their appearances.
I'm left wondering if the mom ever had any hunch her babies had different fathers. I've got to imagine if the dad thought the twins looked too different to be 100 percent related, she had to have picked up on it. Wow, imagine that moment of realization!
Melissa Willets is a writer/blogger and a mom. Follow her on Twitter (@Spitupnsuburbs), where she chronicles her love of exercising and drinking coffee, but never simultaneously.