The 19-year-old anonymous, from Mineiros in Goiás, Brazil, told the Daily Mail that she took a paternity test because she wanted to confirm who the father was.
How did he know?
According to the report, the mother had doubts about the father of her children and to confirm that she had done a DNA test using the sample of the man whom she believed to be the father. After testing, she found that only one of her children showed positive for the DNA test while the other did not. “Then he remembered that he had sex with a different man on the same day and when this other man got tested, he showed he was the father of the other twin,” the report said.
The explanation for this bizarre possibility lies in a biological phenomenon called heteropatternal superfecundation, in which a second ovum released during the menstrual cycle is fertilized by the sperm cells of another male in a separate mating. After fertilization, the babies share the mother’s genetic material, but they grow in separate placentas.
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The phenomenon was initially presented by Archer in 1810. “Although rare in humans, heterosexual superfecundation is common in dogs, cats and cows,” says a report in The Guardian.
Two scenarios can be explained in this: First, a female may release two eggs at the same time. Since sperm can live for a few days, it will be possible to have sex with one expectant father before the egg is released, and the other just after ovulation. In the second scenario, the female releases two eggs within a span of a few days but in the same reproductive cycle.
According to media reports, only 20 more such cases have been reported so far.