Miley Cyrus' parents -- Billy Ray Cyrus and Tish -- are calling it quits after 17 years of marriage. The couple filed divorce docs in Tennessee earlier today -- citing irreconcilable differences. Billy and Tish -- who have 5 children together -- released a statement saying, "As you can imagine, this is a very difficult time for our family. We are trying to work through some personal matters. We appreciate your thoughts and prayers."