A pair of twins has been discovered to have different fathers, after the dissimilarity between the children prompted their parents to take DNA tests.
The children, from Vietnam’s northern Hoa Binh province, are two-year-olds and distinctive by one having thick, wavy hair, while the other has thin, straight hair.
However, the tests, carried out by the Hanoi Centre for Genetic Analysis and Technology, proved that the twins both belonged to the mother.
The 34-year-old husband was found to be the father of only one of the twins, making the children bipaternal.
Bipaternal twins are extremely rare and this is reportedly the first case to be recorded in Vietnam.
Dr Keith Eddleman, director of obstetrics at Mount Sinai Hospital in New York told CNN that it is possible for a woman to conceive bipaternal twins through two acts of sexual intercourse.
A woman’s egg has a life-span of between 12 and 48 hours, he said, while a sperm can last for between seven and 10 days. It is during this overlap that it is possible for two eggs to be fertilised.