Paternity tests are court-ordered and taken for one of two reasons - to prove or disprove biological fatherhood. On a reality-based television talk show broadcast in Washington, a woman wanted to publicly determine the father of her twins. However, to the show's host surprise and to the shock of the mother of the fraternal twins, not one, but two separate men were found to have fathered her children.
When paternity tests identify a man as a father, that man is usually required to pay child support and may receive visitation rights. It will be interesting to see how the results of this paternity test play out in court.
According to Discover Magazine, the occurrence of heteropaternal superfecundation is so rare that only 10 cases have ever been verified. In animal reproduction, it is not uncommon for cats and dogs to produce litters of kittens and pups with different fathers. However, human females, more often than not, produce a single egg and usually mate with just one male during ovulation, the time of greatest potential pregnancy.
There are less common occurrences, as in the case of a human female producing two separate eggs at the same time, which, if fertilized by the sperm of a single male, become fraternal twins when fathered by one man.
Heteropaternal superfecundation takes place when two separate eggs are fertilized by two separate males, an extremely rare event that can occur only if the female has multiple sexual partners during ovulation.
The test for biological fatherhood involves taking DNA samples from a child and the child's probable father or fathers. In the case of the talk-show twins with two fathers, the DNA test showed that the children had a zero percent chance of sharing the same father, while at the same time proving that only one of the twins' biological fathers was able to be identified.
Source: AOL News, "Twins From Different Fathers: Maury Povich's Most Bizarre Paternity Test," 18 April 2011