Spelling, 48, recently posted a holiday card on Instagram with the couple's five children. Of McDermott's absence, she clarified in the comments that the actor was "filming his new feature film in Canada" when the photo was taken. But a source tells PEOPLE she and McDermott, 55, are "not in a good place and have been evaluating their relationship."
"It's been very chilly between them for a long time. They have been through the wringer before, but they've always gotten out of it," the source says of the stars, who previously weathered relationship struggles in the public eye when he admitted to cheating on her in 2014. (Following the affair, the couple documented their life together on their reality series True Tori.)
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"Tori still has major trust issues. Part of their relationship was never fully repaired after he was unfaithful," the source continues. "They've been living separate lives. They will still have family meals and occasional outings, but it's for the kids."
Spelling and McDermott have been married since 2006 and are parents to Liam Aaron, 14, Stella Doreen, 13, Hattie Margaret, 9, Finn Davey, 8, and Beau Dean, 4. As things stand, the source says Spelling "is determined to come out of whatever happens on top," adding, "She's working really hard and has her hands in a lot of things."
Rodin Eckenroth/Getty Images Tori Spelling and Dean McDermott
A second source tells PEOPLE things between the pair have "been bad for a really long time, over a year for sure."
"But Tori doesn't want to break up the family," the source continues. "She thinks the kids need their dad. These are their fundamental years and they've fought to stay together for the kids."
"Dean has a really, really good bond with the kids," the source adds. "He's been a stabilizing force for them."
Still, the source says trust issues are indeed at play: "Tori still has major trust issues with Dean. And he's like, 'We moved on from that.' It's complicated and a very toxic and rocky situation."
Gregg DeGuire/FilmMagic Tori Spelling and Dean McDermott
A third source adds that the Beverly Hills, 90210 alum has been "keeping to herself more as the situation with Dean continues to be so up in the air."
"It's true he has been in Canada filming," the source says. "But [for Tori] being alone with five kids and expected to handle all the day-to-day responsibilities that come along with that really took a big toll on their relationship."
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Spelling has alluded to marriage trouble in recent months. During an appearance on SiriusXM's Jeff Lewis Live in June, the actress revealed the two weren't sleeping in the same bed.
She also previously opened up about her marriage in an interview with PEOPLE in 2016, saying she and McDermott "had to start over" and "completely rebuild" after the cheating scandal.
Over time, and thanks to intense couples therapy and individual personal healing, "we made the conscious decision based on our love for each other to tough it out and work through it," she said. "It was one of the worst times in our lives, but it was also one of the best times. I wouldn't change anything because if we hadn't started talking and opened up those lines of communication, maybe we wouldn't be here today."