Jennifer Aniston once cheated on then-husband Brad Pitt with "Friends" co-star Matt LeBlanc.

According to HollywoodLife, Star magazine makes that explosive claim in a cover story soon to hit newsstands. LeBlanc's father, Paul, apparently serves as the source of the allegation.

"He had fun, that's for sure," the elder LeBlanc said of his son's time on the long running sitcom. "He even had a relationship with one of the girls...Jen. They would make out in the dressing rooms. He told me about it -- it was when she was married to Brad Pitt."

The two stars also briefly had a fling on the show at the end of Season 9 and beginning of Season 10. Pitt's much talked-about relationship with Angelina Jolie didn't start until after then, meaning that Aniston would have cheated first, if Paul's claims are true.

Paul goes on to reveal he and his son has a major falling out three years ago and to this day still aren't on the best terms.

As for the claims regarding Aniston, a rep for the actress told HollywoodLife they are "absolutely 100 percent false. Jennifer has never had a romantic or sexual relationship with Matt LeBlanc."

Pitt, 51, and Jolie are now married and have six children together, while Aniston has been engaged to film star Justin Theroux since August of 2012.

Aniston, 46, has also starred in such films as "Bruce Almighty," "The Break-Up," "He's Just Not That Into You," "The Good Girl," "Marley & Me" and "Along Came Polly."

She and Pitt were married for five years, divorcing in 2005. "Friends" ended in 2004 after 10 years on the air.