The husband was suspicious that one of the boys didn't look like him.

A woman's infidelity surfaced after she gave birth to twin boys with different fathers in an extremely rare occurrence, experts said.

The mother admitted to cheating on her husband after DNA results confirmed one of the twin boys had a different father.

According to experts, the exact odds of the phenomenon, called heteropaternal superfecundation, are difficult to calculate. However, previous studies have shown the chance could be between one in 400 pairs and one in 13,000 pairs, Metro.co.uk quoted The Guardian.

In this case, the husband, known only as Xiaolong, was already suspicious as one of the boys did not look like him. Later, the couple, from south-eastern Xiamen city, China, was required to produce results of paternity test in order to register the birth of their twins. They underwent DNA tests which revealed one of the babies had different biological father, reported Strait Herald.