How Kelsey and Spencer Grammer Mended Their Strained Relationship

The 67-year-old actor and the "Rick and Morty" voice actress have had a strained relationship over the years, after Grammer split from Spencer's mother Doreen Alderman as a child.

Since committing to starring in the Lifetime holiday movie "The 12 Days of Christmas Eve" together, the duo have begun to heal old wounds. In the film, Kelsea and Spencer mimic their own relationship, playing a father and daughter with their own fair-share of issues.

In an interview with PEOPLE, the pair admitted the shortcomings of their relationship and shared how their newest project brought them closer together.

"I certainly regret I let her down a couple of times," Kelsey said, sharing that his work on the cast of "Cheers" in 1984 kept him away from his family. "Obviously she was a child of divorce. It was hard on us. I feel sorry about it, but I'm also thankful that we had a chance to make amends."

Grammer said it was actually his idea for Spencer to play his on-screen kid in the film, a kid who's constantly disappointed by her dad and his inability to be there for his family.

"It seemed like the right idea to me," Kelsey admitted. "I said, we'll have to make sure she wants to, because you never know, we blow hot and cold like all fathers and daughters do."

The 39-year-old actress confessed that she was hesitant about accepting the role, but eventually took it on.

"There's definitely aspects of this movie that resonate with me personally," she explained. "First of all, playing daughter to your actual father is something unique. He's been such an incredible influence on my craft and my performances and also my work ethic, so working with him was actually quite a pleasure."

The “Greek” alum continued, "In ‘The 12 days of Christmas Eve,’ this father and daughter get to repair their relationship at some point. And the dad comes back to really, really figure out what the meaning of Christmas truly is. And honestly for me, for that month that we shot, it was incredibly fun and wonderful to spend time with my dad. I think it was really healing for us."

“So thank you Lifetime, for the therapy!" she laughed.

Kelsey previously opened up to PEOPLE about how his other six children have become a "big part" of this chapter of his life.

"I work on a lot of things. I like the idea of being sort of a magnet. Try this, try that. Some of them don't work out, some of them don't," he noted. "Kids are a big part of it now."

The “Fraiser” alum shares Auden, 5, Kelsey, 7, and Faith, 9 with wife Kayte Walsh. From his previous marriage to Camille Grammer, Kelsey is also father to Jude Gordon, 18, and Mason Olivia, 21. He also had Greer Grammer, 30, with Barrie Buckner.

Fatherhood has "never been better," Kelsey added. "It's the greatest experience in the world, the joy every day of being with my kids."