Heteropaternal superfecundation is the conception by a mother of babies that are genetically half-siblings with different biological fathers.
Known case of heteropaternal superfecundation are very rare; about 19 had been reported worldwide by 2020. It has been suggested that the observed rarity was due to the lack of testing—cases are only discovered when both twins take DNA tests—with many more cases being discovered with the availability of molecular methods and the increasing number of paternity tests.[6]
Heteropaternal superfecundation is common in animals such as cats and dogs. Stray dogs can produce litters in which every puppy has a different sire. Though rare in humans, cases have been documented. In one study on humans, the frequency was 2.4% among dizygotic twins whose parents had been involved in paternity suits.[7]
Cases
In 1982, twins who were born with two different skin colors were discovered to be conceived as a result of heteropaternal superfecundation.[5][8]
In 1995, a young woman gave birth to diamniotic monochorionic twins, who were originally assumed to be monozygotic twins until a paternity suit led to a DNA test. This led to the discovery that the twins had different fathers.[3]
In 2001, a case of spontaneous monopaternal superfecundation was reported after a woman undergoing IVF treatments gave birth to quintuplets after only two embryos were implanted. Genetic testing supported that the twinning was not a result of the embryos splitting, and that all five boys shared the same father.[5][9]
In 2008, on the Maury Show a paternity test on live television established a heteropaternal superfecundation.[10]
In 2015, a judge in New Jersey ruled that a man should only pay child support for one of two twins, as he was only the biological father to one of the children.[11]
In 2017, an IVF-implanted surrogate mother gave birth to twins, one biologically the child of the woman and her husband, and the other genetically unrelated, from an implanted embryo (not superfecundation as such).[12]
In 2019, a Chinese woman was reported to have had twin babies from different fathers, one of whom was her husband and the other was a man having a secret affair with her during the same time.[13]
In 2022, a 19-year-old Brazilian from Mineiros gave birth to twins from two different fathers with whom she had sex on the same day.[14]
A pair of adult English twins who discovered they had different fathers described in 2026 the human implications of the gradual discovery.[15]
