Miley Cyrus' mom had affair with Bret Michaels

Nov 2, 2010 at 7:27 p.m. ET

Sources say that Billy Ray Cyrus filed for divorce from Miley Cyrus' mom, Tish, because he learned she was having an affair with Bret Michaels.

Bret Michaels and Tish Cyrus

Miley Cyrus' parents ended their 17-year marriage because mom Tish, 43, had an affair with Bret Michaels, 47, says US Weekly.

Billy Ray shocked

"Billy Ray was completely unaware of what was going on," a source says.

Bret became "close to the entire family" in February when he and Miley paired up for Nothing to Lose. That is when Tish and Bret started having an affair -- Rock of Love style -- on the sly.

Tish made a public appearance on February 28 with Michaels, showing up at his performance at the Key Club in L.A.

Tish's cheating broke up marriage

Billy Ray found out about the affair (and reportedly one other affair!) and filed for divorce on October 27, seeking joint custody of Miley, as well as 16-year-old Braison and 10-year-old Noah. "It was a professional relationship that turned into something more," says the source.

Bret's rep denies the allegations, saying, "There has never been an affair or a fling," as does Tish's rep.

I wonder what Kristi Gibson, Bret's rumored fiance and mom of their two children together, has to say about this?

More on the Cyrus family: 

Billy Ray and Tish Cyrus file for divorce
Miley Cyrus shocks with new racy video
Miley and Tish Cyrus