Johnny Knoxville discovers he's from 'significant in-breeding'

Jackass star was looking back through his family tree.

It's not the kind of revelations that you'd want airing on an episode of 'Who Do You Think You Are?', but it appears that Johnny Knoxville has made some shock discoveries about his family tree.

The 'Jackass' star was looking into his genealogy hoping to trace the roots of his family.

It was during his search that he was told the extent of his family's rather close connections, with a top US genealogist he had hired breaking the news to him.

[Knoxville: I want Bad Grandpa 2]

“He calls me in... and he goes, 'Sit down, you know in these rural mountain regions you come from, no one ever goes into the community and no one ever leaves the community',” he said.

“'So it's not uncommon that there's in-breeding in those communities'.

“I said, 'Is there in-breeding in my family?' and he says, 'A significant amount'.”

But in typical Knoxville style, he took the news in excellent humour.

[Knoxville positive about Jackass 4]

“I was so happy. He thought he was giving me a really horrible thing and I had tears rolling down my face.”

Knoxville, whose real name is Philip John Clapp, hails from Knoxville, Tennessee.

He changed his name to Johnny Knoxville in part because of his love of country legend Johnny Cash.

Knoxville is currently starring in 'Bad Grandpa', out in UK cinemas now.