People think that Beyoncé’s son’s name confirms a long-running theory about her and Jay-Z

SIR Carter isn't exactly a conventional baby name.

But, then again, Beyoncé and Jay-Z aren't exactly conventional parents.

The superstar duo recently posted a stunning photo on Bey's Instagram to reveal twins Sir Carter and Rumi to the world, a month after they were born.

But Beyoncé's high-profile second pregnancy got a lot of people talking, shining the spotlight on a long-running theory about the mum-of-three's marriage to Jay-Z.

Now we know what Bey's babies are called, fans of the pop pair are pretty sure that Sir Carter's unusual name is the key to solving a long-running mystery.

After the pair's 2008 marriage, fans were left wondering whether Beyoncé had taken her new husband's name.

But a theory swirled that Jay-Z, real name Shawn Carter, instead took his wife's surname, Knowles.

The logic behind this unconfirmed claim was the fact that Bey's parents didn't have any sons, and were allegedly desperate to keep the Knowles name going.

But now, pop fans think Bey has given the game away with Sir Carter's name.

If she did take Jay-Z's surname, Carter, the pair's son would have the full name Sir Carter Carter.

Because that's such an unlikely name, fans now suspect that the babies actually have Beyoncé's surname - making their son Sir Carter Knowles.

However, others have taken to Twitter in their confusion to ask whether Carter could be Sir's surname.

The ridiculously complex dilemma led one fan to tweet: "So, A) Is the first name 'Sir' and the surname 'Carter' or is it 'Sir Carter Carter' B) Is it just Rumi, like Cher or is it Rumi Carter?"

Another asked: "Is naming him Sir Carter Beyoncé's assertion that the twins will take her surname??"

And a third fan tweeted: "Is Queen Bey's baby boy called Sir Carter Carter? Or just Sir, surname Carter. And in a post-Lemonade world why call your boy Sir?"

But this isn't the only aspect of the A-list pregnancy which has fans scratching their heads.

In fact, we recently revealed all the hints you might have missed about Beyoncé’s pregnancy - including how she revealed the gender of her twins.

We also told how the famous couple's kids could be trendsetters already - as a result of Sir Carter's unusual name.