Todd, who turned 55 on Friday, cited “incompatibility of temperament between the parties such that they find it impossible to live together as husband and wife,” according to a copy of the divorce complaint obtained by PEOPLE.
It’s dated Aug. 27, though online court records show it was filed last week. Todd’s attorney in the case previously represented daughter Bristol’s ex-husband, Dakota Meyer, in their split, the Associated Press reported.
The couple, who met in high school, eloped in 1988 and have five children together, four of whom are adults. Todd is seeking joint custody of their 11-year-old son, Trig, according to the complaint, and fair division of their assets.
The couple celebrated daughter Piper’s high school graduation together in May but spent Fourth of July apart: kids Piper, Trig and Willow were with him and daughter Bristol was with her.
“They seemed wonderful together,” Cain said. “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,” Cain continued, “and I’m certain that they’ll both remain dedicated to Trig and their other children.”
After leaving office in Alaska in 2009 — and failing to be elected vice president alongside Sen. John McCain in 2008 — Sarah became a reality TV star and commentator.
A listed attorney for Todd didn’t immediately respond to PEOPLE’s request for comment on Monday; neither did he nor Sarah.