Katharine McPhee, 40, and David Foster, 75, address three-decade age gap after celebrating milestone birthdays

Katharine McPhee and David Foster are marking a year of milestones together. In March, the American Idol alum celebrated her 40th birthday.

In June, the couple commemorated their fifth wedding anniversary. And on November 1, David celebrated his own 75th birthday, capping off a major year for the pair.

David marked his big day with a star-studded concert titled You’re the Inspiration: David Foster at the Hollywood Bowl, which included appearances from Andrea Bocelli, Kristin Chenoweth, Michael Bublé, Charlie Puth, Jennifer Hudson, Tori Kelly, and of course, Katharine herself.

“It’s a big number. It’s exciting,” she told People about her husband’s big birthday. She noted, though, that neither of them take much stock of their ages, which also translates to their relationship, which involves a three-decade age gap.

“Honestly, I think that we’re both very similar in this way,” Katharine noted. “I welcomed my 40s, and David didn’t have any conversations about, like, ‘Oh, I can’t believe I’m 75,’ or I didn’t say, like, ‘Oh, I can’t believe I’m 40. I’m really mourning that.'”

She continued: “We didn’t do any of that. So, we’re kind of both cut from the same cloth. It’s like we sort of just accept life as it comes, and we’re not fighting getting older, because it just keeps getting better.”

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David himself told People at the event about any nerves they were feeling: “She’s fine, and I don’t even think about it either. You know, I’m just groovin’.”

Ahead of the concert, he remarked that it was all “kind of a blur,” adding: “You know, we had a big fundraiser last night, on rehearsal day, on my birthday on Friday.”

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“So it hasn’t caught up with me. I haven’t really celebrated my birthday yet, but last night was a big blowout for my foundation,” he said. “And tonight, of course, is the concert. And I think maybe tomorrow I’ll think that I’ve just turned 75.”

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After the concert, the Canadian musician and producer took to social media to gush: “I could not have asked for a better birthday. Thank you all for coming! And to all my incredible friends for making this happen.”

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Katharine and David first met in 2006, when he was a guest mentor on season five of American Idol, where she eventually finished as the runner-up to Taylor Hicks. David produced her first single after the show as well.

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At the time, however, she was dating Nick Cokas, who had persuaded her to audition for Idol in the first place. She and Nick tied the knot in 2008.

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In 2013, Katharine was photographed kissing her Smash director Michael Morris, but she filed for divorce just a few months later from Nick, citing that they’d been separated for over a year at that point. Their divorce was finalized in 2016.

She reconnected with David, with whom she’d maintained a friendly professional relationship, and they finally embarked on a romance. In June 2018, they announced their engagement, and a year later, they got married in London. They also share a son, Rennie, who is now three years old.