The movie star, 76, has been raising his daughter Carys, 18, with his wife Catherine Zeta Jones, 51.
Despite being one of the biggest Hollywood actors in more than 50 movies, he was not recognised at his daughter’s high school graduation.
Michael was left red-faced when parents assumed he was her grandad but he said he wasn’t taking it personally.
He told The Kelly Clarkson Show : “I gotta tell you, Kelly, it’s a little rough when you’re going out the doors and the other parents are saying, ‘Oh congratulations… you must be so proud of your granddaughter.’
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“I said, ‘Well, I don’t know, man. Yeah, okay.’ I’m not gonna take it personal, they’re just trying to be nice.”
In recent weeks, the proud dad marked the milestone on his Instagram account with a photograph from his daughter’s graduation.
He wrote: “Congratulations to Carys and the entire class of 2021! Your Mom and I are so proud of you!
“We love you so much and we are so excited for your future as the best is yet to come! Dad.”
Michael and Catherine also raised their son Dylan, 20, together; the actor has a son Cameron with his ex wife Diandra Luker.
Elsewhere on the episode, Michael confessed he and Catherine were worried about their children flying the nest.
The proud dad marked the milestone on his Instagram account with a photograph from his daughter’s graduation
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He said: “It’s scary. It really is. You look at each other and go, ‘Well, it’s just you and me, babe.’
“You forget how many conversations you sort of hide behind in terms of talking about your kids and what’s going on next and this and that, and then one day you just look at each other…”
Michael and Catherine have been going strong as a married couple for more than 20 years.
The actor said paying attention to each other over the years was paying off now.
He added: “We’re 20 years now, so all those good years of paying attention to each other are paying off now.”