A young woman who had sex with two men on the same day has given birth to twin boys with different dads.

The 19-year-old mum who lives in Portugal is believed to be only the twentieth known case of heteropaternal superfecundation in the world – where two eggs are fertilised by sperm from different men.

Her unusual situation only came to light after she decided to have a paternity test in order to confirm which one of the men was the father.

“I was surprised by the results. I didn’t know this could happen. They are very similar,” the unnamed woman reportedly told local media.

Her doctor, identified as Tulio Jorge Franco, said that her case is extremely rare – and described it as a “one in a million” situation. Posted By Ghost