Scientists in Vietnam have confirmed an extremely rare case of twins having different fathers. The twins from Hoa Binh province are two years old.

The dissimilarity in the twins’ appearance prompted their parents to go for DNA test. Both the parents underwent DNA test as well for they feared that their baby was switched at birth.

They took the children to the Center for Genetic Analysis and Technologies in Hanoi to have the DNA test. The test showed that there was no switching done by the hospital. Rather, the twin has the same mother but different father, as stated by CNN.

Le Dinh Luong, president of the Genetic Association of Vietnam, said that the family was surprised by the disclosure and is trying to find the best way to deal with the unusual situation.  He further stated that twins with different father are extremely rare case. He also added that this is the first case in the country that he knew of.

He said, “Our Centre for Genetic Analysis and Technology lab has tested and found a pair of bi-paternal twins.”

He added, “This is rare not only for Vietnam, but for the world.”

However, he declined to give more details about the case because of the confidentiality agreement with the parents.

This phenomenon happens when two eggs from the same mother are fertilized by sperm from two different male, during different sexual intercourse within the same ovulation period, as reported by The Telegraph.

A woman’s egg has life span of 12 to 48 hours and a sperm is useful for 7 to 10 days. Thus, there is only a week’s time for possible overlap.

In 2009 a similar case was reported in America when Mia Washington and her partner James Harrison had DNA test after noticing their twins had different facial features.

Mia commented, “Out of all people in America and of all people in the world, it had to happen to me. I’m very shocked.”

In another twin news, Swiss doctors at Bern University Hospital last month successfully separated a conjoined twins.