Hugh Grant had no idea he was related to Love Actually co-star and only found out while filming

Just when you thought you'd learned everything there is to know about everyone's favourite Christmas movie, Love Actually, yet another fun fact surfaces and makes you question your entire fandom to the cult rom-com classic.

From fan theories and age-gap reveals to bombshell revelations made by cast members, and even a modern take on the expansive list of 'red flags' present with many of the characters, it's clear the well of knowledge surrounding the 2003 flick is infinite.

One of the latest bits of Love Actually trivia to make its rounds online reveals that Hugh Grant had no idea he was related to one of his co-stars and, even more interestingly, only made the discovery after filming had already commenced!

Then-13-year-old Thomas Brodie-Sangster, who starred as Liam Neeson's character's son Sam in the movie, reportedly told the Notting Hill and Bridget Jones A-lister, who took on the role of the Prime Minister, that they were distantly related after meeting on the set.

Thomas, who is now 34, was quoted as saying: "His grandmother and my great-grandmother are sisters... [Hugh] didn’t know.

Hugh Grant stars as the Prime Minister in the hit 2003 Crimbo rom-com (Paramount)

"I said, 'Apparently, you are my uncle or my cousin or something'. Then he kind of remembered my mum and uncle. So, for the rest of the shoot, he went round saying 'Hello cousin'. That felt quite cool."

Thomas, who has since gone on to star in a number of Hollywood blockbusters himself, later addressed the familial connection once again during an interview on Lorraine in November of last year.

Thomas Brodie-Sangster revealed he and Grant shared distant relatives (Paramount)

"He referred to me as 'little cousin' while filming Love Actually," the Maze Runner star said. "He’d come and ruffle my hair."

And, while Thomas told Lorraine that 64-year-old Hugh is an 'uncle of some kind' to him, they're actually third cousins according to IMDb.

"Hugh’s maternal grandmother, Margaret Isabel Randolph, was the sister of one of Thomas’s maternal great-grandmothers, Barbara May Randolph," the site states.

Fans couldn't wait to react to the news at the time, with many rushing to social media to share their utter shock.

One X user exclaimed: "THOMAS BRODIE-SANGSTER AND HUGH GRANT ARE RELATED?! THEY ARE FAMILY?! OK, THAT EXPLAINS A LOT, ACTUALLY..."

"Just found out that Hugh Grant and Thomas Brodie-Sangster are related waddaf*ck!!!!" penned a second.

A third chimed in: "Wait Hugh Grant and Thomas Brodie-Sangster are related???? What!"

"OH MY GOD Thomas Brodie-Sangster and Hugh Grant are related???" gushed another.

And a final fan echoed: "Just found out that Thomas Brodie-Sangster and Hugh Grant are related!

"This is so huge I can't even say how ridiculously happy I am!"