News ofSarah Palin‘s pending divorce fromTodd Palincomes as a surprise to many — including friendDean Cain, who had dinner with them at their Alaska home just a few months ago, he tells PEOPLE.

“They seemed wonderful together,” says the actor, 53. “I’d hate to speculate on the cause — what happens behind closed doors, and how people grow and change over time is something no one can ever predict or understand, save those two people.”

“I know that they’re both extremely devoted and wonderful parents,” he continues, “and I’m certain that they’ll both remain dedicated to Trig and their other children.”

“They were so warm and gracious, and completelynormal,” Cain says. (That may have surprised his friends, he says, but not him.)

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He is seeking joint custody of their 11-year-old son, Trig, according to the complaint, and fair division of their assets.

(A listed attorney for Todd didn’t immediately respond to PEOPLE’s request for comment; neither he nor Sarah immediately returned messages.)

The Palins celebrated daughter Piper’s high school graduation together in Maybut spent Fourth of July apart.

The two eloped in 1988 and have five kids together.

“Family is everything to them,” Cain tells PEOPLE. “I just hope they remain civil and good friends throughout this ordeal.”

source: people.com