A mother got the shock of her life when doctors told her that her twin sons came from different fathers.

Mia Washington of Dallas, TX, and her partner noticed that their 11-month-olds, Justin and Jordan, had different facial features. The couple decided to go to a DNA clinic in Dallas and tests showed that there’s a 99.999% chance that Justin and Jordan did not have the same father. After the results, Washington revealed that she wasn’t faithful.

Though Washington’s case is rare, doctors have a scientific name for this: heteropaternal superfecundation. And while this is one of the first real, documented cases made public in recent years, the medical marvel has happened on soap operas. On the NBC soap "Days of our Lives," character Sami Brady mothered fraternal twins born to two different men she slept with — hours apart.

So how does this happen? Sky News’s health correspondent Thomas Moore explains: "A woman can release two eggs from her ovaries, and the eggs will remain viable for 24 hours after ovulation. Sperm can survive up to five days inside a woman’s body, so a woman could sleep with different men several days apart, and get pregnant not once, but twice."

Thus, in this situation, fraternal twins are also half-siblings. (And you thought you had interesting family stories!). Have an odd family story of your own? Tell us about it below.