Here is a bizarre factoid I gained from MSN.com: Apparently, it is possible for twins to have different fathers. It sounded too much like an urban myth so I googled in the information. But other websites confirmed the information in this story and added it was possible for twins of the same father to be of different gestational ages.
Not only is it possible for fraternal twins to have different fathers, it’s on the medical record books. This official medical term for this phenomenon is heteropaternal superfecundation.
The classic case was recorded in 1810 by John Archer, the first doctor to receive a medical degree in the U.S. According to Dr. Archer, a white woman who had sex with a black man and a white man within a short time of each other subsequently gave birth to twins–one white, one mulatto. Other cases have been reported since. And you thought this only happened with puppies?
Sperm cells can live inside a woman’s body for four to five days. Once ovulation occurs, the egg remains viable for another 12 to 48 hours before it begins to disintegrate; thus, the fertile period can span five to seven days.