Citing irreconcilable differences, Bruce Willis, 45, and Demi Moore, 37, who separated in 1998, officially put the wheels in motion last week to end their 13-year marriage. The divorce papers were filed at a courthouse near Sun Valley, Idaho, where they had shared a reputed $6 million estate, reports the Associated Press. Moore still resides in Idaho, where the Willis's three children -- Rumer Glenn, Scout Larue and Tallulah Belle -- attend school. In May of this year, it was reported that Moore and Willis were on friendly terms. Although he was going strong with girlfriend Maria Bravo, 33, a Spanish model turned marketing executive, Bravo told PEOPLE that she, Willis and Moore "spent some time together. She's a very sweet lady, very sweet. Because she has a relationship with someone else, that helps." That person in Moore's life was martial arts instructor Oliver Whitcomb, 30, with whom she is still involved.