Human nature sometimes surprises us. A man did a paternity test for his newborn child and the results showed that the actual DNA in his sperm was not derived from him but from the unborn twin brother who had been absorbed in their mother's womb.
No, this is not a weird science fiction novel. She is a rare, but not unknown-medicine event called chimerism (chimerism).
While many pregnancies start with multiple embryos, often all but one, they are eliminated. But sometimes DNA from the lost brothers is absorbed by the surviving fetus, leaving parts of DNA of in survivor. About one in eight pregnancies involves such a case, although most go unnoticed until it is genetic essay.
The chimera was discovered when parents asked for a clinical fertility test because their newborn son had a different type of blood from their parents. Concerned that the clinic had used the wrong sperm after the failure of the first paternity test, the clinic said they were, in fact, the only white donor on that day, and that their son was Caucasian as they were. The next genetic test by the service 23andMe showed a strange result: the son and father were genetically linked, but his father was genetically his uncle !!!.
Further tests showed that at least the 10 percent of the father's sperm came from absorbing his brother. According to BuzzFeedNews, this is not unheard of, although usually in women they fail in the maternity test.
