Dad orders DNA test, finds out he's the father of only one twin

Article here. Excerpt:

'Vietnam has identified an extremely rare case of bi-paternal twins - twins with different fathers.

A set of twins born to a Vietnamese couple, whose names have not been released, were recently taken for testing because of stark differences in the children's appearances, according to local reports.

"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, told AFP.

"This is rare not only for Vietnam, but for the world," he said, explaining that the two children had different fathers but the same mother.'