Extended family butting in with opinions about your kids is nothing new—but this case in Vietnam is a wild exception. CNN reports that a Vietnamese couple had their 2-year-old twins genetically tested after family members kept harping about how different the children looked. What the Center for Genetic Analysis and Technologies in Hanoi discovered: The twins are bi-paternal, meaning they share only a mother. The revelations about the family pretty much end there. The twins' gender was not revealed, and the only identifying details given by Vietnam's state-run news agency VNS is that the children have very different hair (thick and wavy vs. thin and straight) and live in Hoa Binh province with their 34-year-old father and mother, whose age wasn't given.
Le Dinh Luong, president of the Genetic Association of Vietnam, says he's unaware of any case like this in his country. That hasn't stopped paranoid fathers from phoning the Hanoi center over fears about their twins, reports the Tuoi Tre paper. It's rare, but certainly not unheard of in the US. Last year, a New Jersey judge ruled a man is father to one twin while another man is father to the other, in a case that had child-support implications. The judge in that case cited two other similar court cases, and a 1997 article by identity testing expert Karl-Hans Wurzinger, who testified in the case, put the number of reported paternity cases involving superfecundation (the fathering of fraternal twins by two males) at one in every 13,000. CNN reports that the lifespan of the egg and sperm allow for roughly a week-long period in which a woman could become pregnant through two acts of intercourse. (This man's son was "fathered" by his unborn twin.)