Why Matthew McConaughey is convinced there's a strong possibility Woody Harrelson could really be his brother

Matthew McConaughey is adamant he could be related to Woody Harrelson.

The two Hollywood stars, who starred in the hit crime TV drama True Detective together, have long been close buddies - as far back as the 1990s.

Over the decades, the pair have joked that their bond has transcended friendship, stating they're closer to brothers.

So, it's fitting the pair are set to star in a TV comedy called Brothers, a fictionalized story of their lives where they decided to live together with their families at McConaughey's Texas ranch.

However, there could actually be an element of truth to the claim.

The possibility was unearthed during a conversation they shared with McConaughey's mom, Mary.

"My kids call him Uncle Woody," the Dallas Buyers Club star said during an episode of Kelly Ripa's Let’s Talk Off Camera podcast. "His kids call me Uncle Matthew. My family thinks a lot of pictures of him are me. His family thinks a lot of pictures of me are him."

They have shared a lengthy friendship (Mark Davis/NBC/NBCUniversal via Getty Images)

Then, McConaughey said his mom blurted out a suspicious claim when the trio were talking about how close they were while on vacation in Greece.

"And my mom is there, and she says, ‘Woody, I knew your dad’. Everyone was aware of the ellipses that my mom left after ‘knew’. It was a loaded K-N-E-W," he said.

Rousing suspicions even further, the pair both hail from Texas, were born in the 1960s and undoubtedly share some physical similarities.

McConaughey said in another interview with Access Daily that when they quizzed Mary, she simply said: "‘Just saying, we might have frequented the same similar place out in West Texas one time when he was on furlough.’"

He continued: "And we all went, ‘What? What, are you going to leave it there?’

"Now we gotta go do some DNA tests."

Harrelson and McConaughey then pieced together that it might have been possible that Mary, who was going through a divorce at the time, might have slept with Harrelson's father, convicted hitman Charles Harrelson.

The pair in EDtv in the 1990s (Universal/Getty Images)

Then during an appearance on British station Radio X, host Johnny Vaughan asked: "Woody, I know you're doing this thing Brothers with Matthew McConaughey. Did you investigate whether the two of you might actually be brothers or related?"

The Hunger Games star replied: "Well, we haven't done the DNA test, but we're probably going to do that. I think there's a real possibility."

The actor fell short at giving an exact date on when they might actually do the test, though.

Still, Harrelson said McConaughey discovering the pair are actually brothers would be a 'much more big deal'.

Speaking on The Late Show with Stephen Colbert, he said: "I mean, he feels like he is losing a father. But I’m like, no, you’re gaining a different father and a brother."