In what sounds like a soap opera storyline or episode of Maury, a Washington man's twin is his baby's biological father. The only problem? He doesn't have a living twin.
How does something like this happen? About one in eight single childbirths may have started as multiple pregnancies. Sometimes, the dead cells of the sibling who doesn't survive is absorbed by the sibling who lives. In this case, the unnamed man absorbed his twin's DNA while in the womb; the DNA in the man's sperm came from his twin, who is the genetic father of his baby son.
First reported by Buzzfeed News, the Washington man and his wife were surprised when their son's blood type didn't match either of theirs. Because the baby was conceived with the help of a fertility clinic, the couple feared that there was a sperm mix-up.
After a failed paternity test, the couple sought a more detailed test. When that test also came back negative, they approached Barry Starr, a geneticist at Stanford University. Starr suggested a genetic ancestry test for the father and son. The results confirmed that the man was actually his baby's uncle.
“That was kind of a eureka moment,” Starr told Buzzfeed News that he realized this might be a case of chimerism, when a person is composed of two genetically different types of cells. “Chimera reports are very rare, but they are real.”
Michael Baird of DNA Diagnostics Center in Fairfield, Ohio, said a test of the man's semen found that about 10% of its cells were a genetic match to his son, “The sperm showed [the father] was indeed a genetic chimera," he told BuzzFeed News.