In an article in the UK's Mirror, a woman takes to social media to write about how her mother-in-law was accidentally exposed after she demanded that her grandchild get a DNA test.
The woman posted the story on Reddit.
It all started when the woman gave birth to her daughter. The child came out with green eyes and it was a characteristic that no one in the family had.
"The reason - she has green eyes. My husband and I don't have green eyes, my parents don't either and neither do my in-laws - no one in my family has them.
The mother-in-law began to suspect that her daughter-in-law may have cheated on her son.
She demanded that the child get a DNA test. After much persuasion, the woman wanted to put her mother-in-law's fears at rest so she had her child and husband get DNA tested.
The results were as expected in that the DNA test confirmed that the woman's husband was indeed the father of her child and she had not cheated on him.
However, the DNA test also exposed a shocking family secret that had to do with the woman's mother-in-law.
The results indicated that the woman's father-in-law was actually not her husband's biological father.
"Our daughter is his but my father-in-law isn't my husband's father," she added.
"My in-laws have been married for decades so the idea that my mother-in-law cheated on my father-in-law never crossed either of our minds.
The tables were turned and now it was very possible that it was the mother-in-law who had cheated on her husband.
The woman and her husband kept this part of the DNA results a secret from the mother-in-law. They want to wait before they confront her because the repercussions could become very serious for the family.
Now viewers on social media are commenting that the mother-in-law should never have demanded a DNA test for her grandchild as it was she who had the secret to hide.
"What gets me is the fact that she pushed for you and her son to do the one thing that would expose her secret.
"All she had to do was keep quiet and no one would’ve been the wiser."