Just one week after Miley Cyrus' parents Billy Ray and Tish filed for divorce, Star Magazine is reporting a surprising reason for the split--Tish's alleged affair with rock star Bret Michaels. And PopEater has an exclusive look at Star's cover.

"Billy Ray suspects there's been something going on between his wife and Bret for a long time," an insider tells Star. And according to the source, Tish is just Michaels' type: "skinny, big boobs and blonde hair." Tish, the source continues, wasn't innocent. She "would always show up to the studio in tight jeans and revealing T-shirts and flirt shamelessly with Bret."

Another source close to the situation tells UsMagazine.com that Michaels "became close to the entire family" while he and Miley recorded and released the racy duet 'Nothing to Lose' earlier this year. It was during that time that Michaels and Tish began seeing each other.

Billy Ray was "ashamed of Tish's behavior and he wants out of this mess," a source said. The country crooner is seeking joint custody of their three minor children, Miley, 17, Braison, 16, and Noah, 10.