A Vietnamese couple had their set of twins undertake genetic testing, because of stark differences in the children’s appearances, with a remarkable and rare outcome.

“Our Centre for Genetic Analysis and Technology lab has tested and found a pair of bi-paternal twins,” Le Dinh Luong, president of the Genetic Association of Vietnam, said. “This is rare not only for Vietnam, but for the world,” he said.

Bi-paternal twins occur when the two children have different fathers, but the same mother. This can happen if two eggs from the same mother are fertilised by sperm from two different men during separate acts of sexual intercourse within the same ovulation period.

According to the Tuoi Tre newspaper, the genetic testing was at the request of the husband, to determine if in fact he was the biological father of both his wife’s twins.  Reports say that relatives of the man pressured him to have the tests conducted due to the striking differences in the now two year old children.

The results indicated the man was related to only one of the babies, with his wife being the biological mother to both children.

According to Dan Tri online news site, the twins were the same sex, born on the same day, just a few hours apart, but looked completely different.

Another rare case of bi-paternal twins was reported in the United States last year, when a court ruled that a man was only required to pay child support for one girl in a set of twins after DNA tests proved he was not the father of both.

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