Bret Michaels and Miley Cyrus perform in Central Park on...

Bret Michaels and Miley Cyrus perform in Central Park on "Good Morning America" on June 18, 2010. Credit: AP

The cause of Miley Cyrus' parents' impending divorce is her mother's affair with rock star Bret Michaels, a source said Tuesday.

Reality TV star and Poison lead vocalist Michaels, 47, "became close to the entire family" in February when he and "Hannah Montana" star Cyrus, 17, released the duet "Nothing to Lose," an insider told Us magazine in a report in Wednesday's new issue.

Michaels and Leticia "Tish" Cyrus, 43, who has been married to country singer Billy Ray Cyrus for 17 years, soon began an affair.

When Billy Ray Cyrus, 49, learned of this and at least one other fling, the magazine said, he filed for divorce on Oct. 22, as previously reported.

"Billy Ray was completely unaware of what was going on," the source said.

A representative for Michaels denied the allegations, telling Us, "There has never been an affair or a fling." Tish Cyrus' representative also issued a denial, though the magazine's source insisted, "It was a professional relationship that turned into something more."

SUBSCRIBE

Unlimited Digital AccessOnly 25¢for 6 months

ACT NOWSALE ENDS SOON | CANCEL ANYTIME