Katharine McPhee, 40, and David Foster, 75, Aren't 'Fighting' Age as They Celebrate Milestone Birthdays (Exclusive)

Age is nothing but a number for Katharine McPhee and her husband, David Foster.

The record producer and composer celebrated his 75th birthday on Nov. 3 with a star-studded concert, You're the Inspiration: David Foster produced by Live Nation-Hewitt Silva, at the Hollywood Bowl, and his wife was one of many to mark the special occasion with a performance.

"It's a big number. It's exciting," McPhee tells PEOPLE of Foster's milestone birthday show, which also featured vocalists including Kristin Chenoweth, Josh Groban, Andrea Bocelli, Michael Bublé, Jennifer Hudson and more.

Foster's 75th birthday arrives after McPhee turned 40 in March, but according to the American Idol alum, they don't make a big deal of the numbers.

"Honestly, I think that we're both very similar in this way," she says. "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.'"

McPhee — who married Foster in 2019 — adds, "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."

Foster shares 3½-year-old son Rennie with McPhee, 40. He’s also father to daughters Allison, 54, Amy, 51, Sara, 43, Erin, 42, Jordan, 39, from previous relationships.

In a separate interview with PEOPLE at the event, Foster shared a similar sentiment about any potential nerves he and McPhee felt about the major birthdays.

"She's fine, and I don't even think about it either," he said. "You know, I'm just groovin'."

As for Foster's birthday celebrations outside of the Hollywood Bowl, he told PEOPLE, "It’s kind of a blur."

"You know, we had a big fundraiser last night, on rehearsal day, on my birthday on Friday," he said. "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."

Foster continued, “And tonight, of course, is the concert. And I think maybe tomorrow I'll think that I've just turned 75.”