Kevin CostnerandChristine Baumgartnerhad a prenuptial agreement in place prior to the recent divorce filing.

In her filing, Baumgartner, 49, listed their date of separation as April 11, and she requested joint custody of their three children: Cayden, 16 on Saturday, Hayes, 14, and Grace, 13 next month.

Costner, in his response filed Tuesday, also asked for joint custody and cited irreconcilable differences. The actor/director’s filing also mentions a prenup, in regards to spousal support, legal fees and properties.

A source tells PEOPLE that divorce wasn’t Costner’s idea: “It was not anything that he wanted or sought, and if he could change the situation, he would.”

Christine Baumgartner and Kevin Costner.Mediapunch/Shutterstock

Inside Kevin Costner and Christine Baumgartner’s 18-Year Marriage Before Their Breakup

They also add, “Pursuant to the terms in Paragraph 9.A. of the parties' Premarital Agreement, Petitioner to vacate Respondent’s separate property residences.”

Costner was previously married to Cindy Silva for 16 years before their divorce in 1994 — which reportedlyresulted in an estimated $80 millionsettlement to his ex-wife.

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Michael Tran/FilmMagic

Kevin Costner (R) and Christine Baumgartner arrive at the Los Angeles premiere of “3 Days To Kill” held at ArcLight Cinemas on February 12, 2014 in Hollywood, California

The pair got married on Sept. 25, 2004. In a statement Tuesday, Costner’s rep said, “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. We ask that his, Christine’s, and their children’s privacy be respected as they navigate this difficult time.”

In November, Costner told PEOPLE about raising a family with Baumgartner. He said at the time, “The house is prettier because of her. Everything is warmer because of her. There’s these little things that she does — and I think it’s the power of love — but that she makes her home that way.”

The actoradded of what he learned from fatherhood, “The world doesn’t revolve around you. It just doesn’t revolve around you. I work as a provider. I’m a father and I’m a husband, but it doesn’t revolve around me.”

source: people.com