Christine Baumgartner, who married Kevin Costner in 2004, filed for divorce on Monday, ending 18 years of marriage. The two started dating in 2000 and tied the knot at Costner's Aspen, Colorado ranch in 2004. The split is said to be due to irreconcilable differences, with Baumgartner asking for joint custody of their three children - Cayden, 15, Hayes, 14, and Grace, 12. Costner filed his response to the divorce yesterday, and he is also seeking joint custody of their children.