The DNA test revealed that twins have different dads, exposing the wife's secret one-night stand.

Promising to love someone for better or worse is one of the most beautiful things we can do.

However, life doesn't always turn out the way we planned because Infidelity isn't something you can just let slide. Also, being the victim of a cheating partner is extremely painful.

One woman in China could never have imagined what her secret affair would lead to. She became pregnant with her husband and her lover—at the same time!

What's even worse, the husband didn't know until after the babies were born.

The bombshell came to light after the couple requested a paternity test so they could register the twin boys with authorities in Xiamen.

However, the results proved shocking as they showed one boy wasn't related to the man who had assumed he was the dad.

It turns out the wife had kept her adulterous ways under wraps, with her husband believing both twins were his.

The dad, however, had long wondered why his twins didn't look alike.

According to the Chinese newspaper Strait Herald, one child had different eyes, mouth, and nose. He also didn't resemble the dad in any way.

Even so, the man never considered the possibility of not being the boy's biological dad.

According to experts, the chance for such a case to happen is one in 10 million.

The rare case is known as 'double pregnancy' or heteropaternal superfecundation. It happens when the ovary releases two or more eggs in the same cycle, and sperms from different fathers fertilize each one of them at the same time.

According to The Conservation:

"It may sound impossible, but twins being born with different fathers is a rare occurrence known as heteropaternal superfecundation."

"Cases only come to light when suspicious relatives request a DNA test of a newborn."

"But one study suggests heteropaternal superfecundation may affect as many as one in 400 twin births in the US."

"It occurs when a mother releases two eggs, and then two sperm cells from different men fertilize them."

"Women have to have sex with two different men within a day before or after ovulation for both eggs to fertilize."

"Although such cases are rare in humans, they're common in other animals, including dogs, cats, cows, and rodents."

"In species where females have multiple partners, some males have even developed strategies to ensure their sperm reaches the egg."

"This may include evolving penises that damage the female's reproductive tract, preventing subsequent mating, as seen in dragonflies."

Following the expose, the wife tried to blame her husband at first. She even accused him of tampering with the results of the test.

However, she confessed to cheating, saying she had had a one-night stand with another man.

In the end, the husband said he was happy to raise his child, but not the one from someone else.