Matthew McConaughey is refusing to take DNA test to finally put to rest long-running rumours Woody Harrelson is his brother.

The actors - famed for their onscreen partnership in True Detective - have leaned into the gossip about their parentage by making new Apple TV+ comedy Brothers which explores the potential family links and Woody has now insisted he is convinced Matthew really is his secret sibling but the Interstellar star won't take a test to prove it.

In a joint interview with The Hollywood Reporter, Woody said; "He won't take the test," and Matthew added: "If we do the test and, say it's true - which it's not - [but if it is], then I've got to unpack 56 years of who I thought my dad was.

"But the worst-case scenario is actually if it's not true, because he's [Woody is ] gonna be horrible to be around."

Rumours about a family connection have circulated for years, fuelled by stories involving Matthew's mother and Woody's father, and the Cheers star is adamant the gossip could be true because it's a fact that their parents knew each other.

He said: "Because Ma Mac did say: 'I knew … your father."

Matthew then insisted he won't take a DNA test to find out for sure because he's convinced his pal won't believe the result if it comes back negative.

He explained: "For him, [it] means more than a DNA test. And if a DNA test comes out and says we're not brothers, he's gonna say: 'That's why you can't trust science'."

Woody told the publication that he would be sad if he found out they aren't actually related, telling the publication: "Oh yeah, I'll be depressed for a while. It's a lose-lose situation.

"It's nice to think of him as my brother. He is more my brother than my brothers in reality, for years and years.

"But when I found out that he's actually my brother - and by the way, there was more to it than just that one statement. And I didn't tell him, but I talked to her [Ma Mac] later. I got certainty that those guys were, uh, you know."

Matthew added: "Listen, don't think science doesn't matter in this, but inclination of words - like K N E W … knew …

"That ellipses is what sealed it for him. And then the fact that my mom has gone on to say that when she went to go to the hospital to give birth to me and she called my dad, and my dad said: 'Oh, I'm not showing up at the hospital, Kay. That ain't my boy.'

"He [Woody] loves that line ... "