The roller-coaster relationship between Sean Penn and Robin Wright Penn may finally be coming to the end of its track. Robin Wright Penn filed divorce papers in Marin County, Calif. on Aug. 12, marking the third time the couple has initiated proceedings to end their marriage. "Irreconcilable differences" is listed as the reason for the filing, and the estranged couple has already agreed upon a division of property and a plan to share custody of 16-year-old son Hopper Jack. The Penns have been together since 1989 and married since 1996. Wright Penn said she does not foresee a reconciliation with her husband: "I hit that crossroad a while ago," she told More magazine in its September issue. "I know what I don't want."