For many around the world, they spend years wondering about their family history and where they come from.
But for one woman, her pursuit of answers led her to a shocking revelation that changed her life forever.
Matilda took to TikTok to detail her eye-opening discovery after her boyfriend got her a DNA-testing kit for her birthday.
The 22-year-old Canadian woman explained that her mum is adopted and she never knew her biological father.
"So I was mostly interested in the health info to see if there was anything to watch out for."
At the same time, her boyfriend also purchased a test for himself.
But after looking at the results, they made a worrying discovery.
"So we got the results back a month later and I was looking through the list of genetic relatives because the only person that I know that I'm technically related to is my mum," Matilda says in her TikTok.
"And I scrolled down and turned to my boyfriend at the time and said, 'hey this is pretty nifty, I'm related to someone with the same name as you.'
"AND THAT'S HOW I FOUND OUT I WAS DATING MY COUSIN."
Her video has since been viewed more than 500,000 times.
In later posts, she explained they originally thought she and her boyfriend were third cousins.
But after doing more digging, a more confronting revelation surfaced.
"I was able to do a bit of research into my father's side of the family and I found someone that had done a genealogical report back to the 1500s," she added.
"Based on the info from that person's research, as well as the percentage of DNA my ex and I shared which was a bit too high to be cousins, I'm fairly confident we are actually second cousins, related through my paternal great grandmother."
She added: "My ex is a great guy and I still care for him deeply, but yeah ..."
The couple has since broken up due to a number of issues, including the DNA test revelation.
A number of viewers expressed their shock and sympathy for the pair.
"As soon as you said he got one for himself I knew it would be something like this," wrote another.
Another said: "My parents found out they were cousins too and well, they didn't stop dating cause obviously I'm here."
"My aunt and uncle didn't find out they were cousins until they had been married like 10 years," a third wrote.