Malcolm McDowell Reveals What Has Kept His Marriage to Kelley Kuhr Strong for Over 30 Years (Exclusive)

Malcolm McDowell is spilling his marriage secrets.

While chatting with PEOPLE about his newly released movie Et Tu, the Hollywood veteran, 82, also opened up about his family life and three decades of marriage with his wife, Kelley Kuhr.

When asked about the secret to a longterm love, McDowell, who tied the knot with Kuhr in 1991, offered a humble response. “You know what? Honestly, I am not an expert on relationships,” the star tells PEOPLE, adding, “I wish I was.”

“And I think just liking the partner you’re with is very important and just respecting,” he says, adding that he is “very lucky” in that department.

“My wife’s a brilliant designer and at the moment, she’s doing this house in Mexico, which is her masterpiece. It’s an amazing thing that she’s done and I’m so proud of her,” he adds of Kuhr.

The Tank Girl actor went on to point out that while he and his longtime love are not in the same field of work, they do have some shared loves — including spending lots of time in antique shops.

“She doesn’t do what I do, but she’s just as successful in her own way and I’m in awe of what she does. It’s amazing. I don’t know how she does it, but she does it,” he says of the designer. “But we also, we’re collectors.”

“We collect stuff,” he tells PEOPLE, “and we pretty much collect and like the same stuff, which is lucky.” That, and it’s “a lot of fun,” he adds.

The couple “always have fun wherever we go,” says the Hollywood vet “always straight to the antique shops and hunting around and having fun that way. It’s great.”

Malcolm and Kuhr are also parents, sharing three sons: Beckett, 21, Finn, 18, and Seamus, 16. He is also a dad to daughter Lilly, 44, and son Charlie, 42, with ex-wife Mary Steenburgen, and a grandfather to four girls.

Elsewhere in his chat about Et Tu, the actor opened up about his “absolutely gorgeous” baby granddaughter, Tove, whom his son Charlie recently welcomed with his wife, actress Lily Collins. The couple announced that they had welcomed a daughter via surrogate in January.

“She’s absolutely gorgeous,” McDowell tells PEOPLE of the little one. “Absolutely beautiful.”

Of his granddaughters, the actor says, “I love being around them and just watching the antics that go on and the dynamic and the difference between them all. It’s staggering.”

Never miss a story — sign up for PEOPLE’s free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer​​, from celebrity news to compelling human-interest stories.

“They’re so different in personality and everything. It’s just beautiful to watch,” he adds.

Et Tu is available to stream and purchase now.