In what may be a first of its kind in Vietnam, a mother has learned that her twins have different fathers.
Relatives insisted that fraternal twins from Hòa Bình province in Vietnam did not look alike so they were taken in for DNA tests in Hanoi according to The Guardian.
One of the infants has thick, curly hair and the other has thin, straight hair.
It was later revealed that the siblings are actually bi-paternal twins, or twins who have different fathers.
Professor Le Dinh Luong, who did the DNA testing, told the BBC that the results were "100 percent correct."
"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," Luong said.
Luong also 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.
Further details were not provided because of client confidentiality.
There are fewer than 10 documented cases of bi-paternal twins worldwide.
