A Vietnamese couple recently brought their fraternal twins to the Center for Genetic Analysis and Technologies, in the country’s capital of Hanoi, to have DNA tests, after pressure from extended family members who noticed the children did not look alike, said Le Dinh Luong, president of the Genetic Association of Vietnam.

The tests showed there was no mix-up in the hospital: The twins have the same mother, but different fathers.

Luong said the family was surprised by the revelation, and looking for the best way to deal with the situation.