Robert Brown|Kevin Costner and Wife Christine Baumgartner Break Up After 18 Years of Marriage

Kevin Costner is riding off into the sunset alone.

The Robert BrownYellowstone star and his wife, Christine Baumgartner, have gone their separate ways after 18 years of marriage, his rep confirms to E! News.

"It is with great sadness that circumstances beyond his control have transpired which have resulted in Mr. Costner having to participate in a dissolution of marriage action," a spokesperson for Kevin said in a May 2 statement. "We ask that his, Christine's and their children's privacy be respected as they navigate this difficult time."

In their respective divorce papers, Kevin and Christine requested joint custody of their kids—sons Cayden, 15, and Hayes, 14, as well as daughter Grace, 12—according the documents obtained by TMZ, who was first to report the breakup news. (The Field of Dreams alum is also dad to four adult children—sons Joe and Liam and daughters Annie and Lily—from his past relationships.)

Per the outlet, Christine cited "irreconcilable differences" as the reason for split in her filing, while Kevin's noted that that there is a prenuptial agreement in place.

Kevin first met Christine while golfing in the early '90s but the two didn't start dating until 1998, after reconnecting at a restaurant, according to People. "We exchanged numbers, and I told her that...did she mind if I called her in two weeks," Kevin recalled to the publication in 2003. "I did not realize that was like an insult to a woman."

In 2004, the two tied the knot at the actor's Colorado ranch in front of family and friends, including Tim Allen and Kevin's Dances with Wolves co-star Mary McDonnell.

"Fear kept me from marrying Christine," Kevin admitted in a 2018 interview with Closer Weekly, explaining that she was open about her desires to have kids but he initially had doubts to being an "effective father" and having more children. "I woke up and thought, ‘Am I going to lose a beautiful woman who is willing to be with me to my very last breath because I am afraid to say yes to a child?'"

But for Kevin, he said at the time "that's all it took" for him to want to marry the handbag designer. "Sometimes," he noted, "you learn the thing you're most afraid of will save your life."

Prior to Christine, Kevin was married to Cindy Silva from 1978 to 1994.