After a woman from New Jersey applied for child support, the authorities ran a paternity test to determine whether the man she was dragging into court was really the father of her non-identical twins. It was then found out that the man had fathered only one of the twins.
If non-identical twins come to be after two eggs are fertilised by two sperms, how about having the two sperms from different fathers? Actually, this is scientifically possible, as proved by a case from New Jersey. A mother who had applied for child support found out that her non-identical twins were fathered by two different men. The medical term for this phenomenon is called heteropaternal superfecundation.
For this to happen, the two male partners must have had sex with the female one within one week because sperms are viable for only about five days. So, a sperm of the first man fertilises one of the woman’s eggs, while a sperm from the second man fertilises a second egg of the woman.
Though this might sound surprising, it is actually as feasible as the case of two non-identical twins fathered by a single man, whereby 2 different eggs from the same woman are fertilised by two sperms of the same male partner.
Would this be a rare occurrence? Given the circumstances that result in this type of pregnancy, it is hard to tell whether it is rare or not. Mostly, these cases only become known when a paternity test of the twins are requested, like for legal procedures.
From a study done 2 decades ago, in 1992, it was revealed that of all the cases pertaining to twins and paternity test requests, superfecundation accounted for 2.4 % of them. This figure cannot be extended to the general population though because the study is about people who asked for legal assistance only. How about those who have not had any paternity test done as part of legal procedures? Hence, it is difficult to tell. Furthermore, generally, people rarely do paternity tests.