A set of twins with different fathers have been confirmed by a local genetic association in Vietnam. The twins had their DNA tested after their family noticed they looked different, according to Atlanta Journal Constitution.
The twins occurrence, known as heteropaternal superfecundation, is rare with few publicly known about. It happens when a woman’s eggs are fertilized by two different fathers within a short period of time.
Professor Le Dinh Luong, president of the Hanoi-based Vietnam Genetic Association which did the DNA testing, said the results were “100% correct” in what he called “an extremely rare case.”
The twins with different fathers, who are now two years old, were born the same day and have the same gender.
Long said bi-paternal twins could happen if two eggs from the same mother were fertilized by sperm from two different men within one to seven days apart in an ovulation period.
“There are only less than 10 known cases of twins with different fathers in the world. There might be other cases but the parents and/or the twins were not aware of it or didn’t want to announce it,” he said in a statement.
He declined to give further details citing client confidentiality, but added that local reports stating the twins’ location, names and timeframe were inaccurate.
To rule out a hospital mix-up with twins with different fathers, DNA testing of the mother showed that she was the mother of both children. Vietnamese news outlets began reporting on the case earlier this month, saying that relatives had noticed that one of the twins looked markedly different from its sibling and parents.