For most people, the discovery that you might be related to your long-time partner - even distantly - would lead to a pretty swift break-up.
The couple recently uploaded a TikTok video to their 560,000 followers, in which they ask 'should we take a DNA test?'.
Having accrued over 6 million views at the time of writing, it's certainly caused some debate - and disbelief - online.
In the TikTok, a caption above the pair reads: "When you find out two years into dating that your mom slept with the same guy."
The account, called 'Carleyandmercedes', then asks their fans the question: "If we're actually related is it wrong to stay together?" in the comment section.
The vast majority of their followers arrived at a clear and unwavering 'no' in response.
Several users implored the pair to take a DNA test in order to try and ascertain whether they actually are related.
“Take one immediately,” one person urged, with Carley and Mercedes responding, “We’re scared.”
“I have no idea who you guys are and I immediately thought you were sisters before reading the text,” one user added.
“That could explain why you two look like sisters,” another TikTok user wrote.
“Am I the only person who thinks that regardless of the results it doesn’t matter?” a different person countered with. “At that point, blissful ignorance will go a long way," they continued.
Carley and Mercedes have already capitalised on the ambiguity of their relationship, having set up an OnlyFans account under the rather crude @Notyouraveragesisters username.
In a more recent TikTok video, uploaded this past weekend, the pair provided their bemused fans with an update, claiming that they have now ordered DNA tests which are yet to arrive.
They aren't the first couple to go viral on TikTok for similar reasons, either.
Back in 2020, Diana Camila Avila and Jordie Vena made headlines for being in a relationship despite being 'step-siblings'.
The couple started off pretty much like any other couple trying to get TikTok famous, with clips involving dancing, cosplay and comedy skits based on their relationship, but they caused quite a stir when they later revealed that they're actually step-siblings.
Speaking to LADbible in 2020, Diana said: "We met six years ago but we started dating three years ago. We met through our parents."
She went on to say that it was 'love at first sight' but because of how they met they both kept their feelings quiet.
However, one night, while their parents were away the pair ended up kissing...and the rest is history.
Featured Image Credit: @carleyandmercedes/TikTok