According to a Chinese newspaper, a DNA test confirmed a woman gave birth to twins with different fathers. I admit I was skeptical when I read about it, but believe it or not, it is possible for twins to have two fathers, although it is rare. (1)
Paternity Test Proves “Bipaternal” Parents
The true paternity of the two babies was confirmed when the couple produced a paternity test to register their twins at the local police station. Paternity tests are commonly requested to prove parenthood in Xiamen city where the couple resides. While you would think the results would be shocking to the parents, the fact one of the boys did not have a biological relationship to the father simply confirmed the father’s suspicions. (1)
Father Suspected Mother
It is reported the father, Xiaolong, was highly apprehensive when he saw the twins were not identical. He couldn’t shake the feeling one of the infants did not look like him. Because the police required the DNA test, the father was able to confirm his fears. (1)
According to a director at the Fujian Zhengtai Forensic Identification Centre, Mr. Zhang, the father was furious when he read the report. However, in an attempt to cover up her guilt, the mother actually accused her husband of falsifying the test results. When her husband persisted in questioning her, the mother finally confessed to having a one-night stand. (1)
Heteropaternal Superfecundation
While this might sound impossible, it is a phenomenon called ‘heteropaternal superfecundation’. It is rare and can only occur when a woman has intercourse with two men within a day. It can happen with the same father or two separate fathers. The woman must be pregnant at the time the second father impregnates her. If she ovulates after she is already pregnant, it is possible for an egg to be fertilized by another sperm. There have even been rare cases where it happens as much as months after the first egg is fertilized. This, of course, would cause the two babies to develop at different rates. (1, 2)
More Common In Other Species
Heteropaternal superfecundation is more common in animals such as dogs, cats, cows, and rodents where females tend to have multiple partners. Some species, because this is possible, have evolved to prevent this from happening. For example, dragonflies have penises that actually damage the female’s reproductive tract so that another dragonfly cannot impregnate the female. (1)
One Pair In 400
Without recent studies available, it is hard to determine how often human heteropaternal superfecundation occurs. However, if we look at the last study performed back in 1993, at least one dizygotic (DZ) twin maternity in twelve is preceded by superfecundation. Common factors include rates of infidelity and promiscuity and in the U.S. among DZ twins born to married white women approximately one pair in 400 is bipaternal. The study noted that in some select groups, such as prostitutes, occurrences could be even higher. (3)
While the headline smacks of sensationalism, this is just another example of truth being stranger than fiction.
