Brad Pitt Hoping for a 'More Positive Year' as He Turns 58: 'His Kids Matter the Most,' Says Source

A source tells PEOPLE Brad Pitt plans on "just sort of hanging out" for his 58th birthday on Saturday

Brad Pitt. Photo: Gregg DeGuire/Getty

Brad Pitt is keeping it "low-key" for his birthday weekend.

The two-time Academy Award winner doesn't intend to go all out with the festivities when he marks his 58th trip around the sun on Saturday. "He plans to have a low-key birthday. Just sort of hanging out," an insider tells PEOPLE.

"He's staying low-key in general. That's really the kind of guy he is anyway," the source says, adding that since his birthday is at the end of the year, "it's a natural time for reflection for him."

Pitt has had a busy year, filming two movies with Sandra Bullock. He makes a cameo in her upcoming romantic comedy adventure The Lost City, which also stars Channing Tatum; and, along with Joey King and Bad Bunny, he and Bullock also filmed Bullet Train in Los Angeles earlier this year.

"It was a challenging year for everybody with COVID and filming amidst that," says the source, adding that the actor is looking forward to 2022.

Pitt — who has been in an ongoing custody battle with ex-wife Angelina Jolie since their split in 2016 — is "trying to stay positive and think about next steps and look ahead and hopefully have an even more positive year," the source explains.

The Ocean's Eleven actor is father to six children, Maddox, 20, Pax, 18, Zahara, 16, Shiloh, 15, and 13-year-old twins Vivienne and Knox, with Jolie.

"The situation with the kids is still a difficult situation," says the source. "It sucks. It is what it is. His kids matter the most to him. But there are just processes you have to go through."

Fortunately, he has a solid support system to lean on. "He is genuinely beloved," the insider says. "People really like him, and he does have a strong circle supporting him."

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The Once Upon a Time... in Hollywood actor has previously been open about aging in the industry. In January 2020, Pitt joked that he was "old" in his acceptance speech for the Maltin Modern Master Award at the Santa Barbara International Film Festival.

"It's things like this and nights like these that tell me that I'm old," he joked at the time. "I've been around a while and I've been doing this for a bit."

He explained all the ways he can tell he's growing older: "I can't stand night shoots anymore, and I'll gladly hand a stunt over to a stunt man. I no longer remember the first rule of Fight Club," Pitt quipped, referencing the famous line from the 1999 movie.

"But it's also nights like this where I get to look back and I feel really, really blessed," he went on. "I feel so fortunate to all the amazing people I've been able to work with who have taught me so much and who've touched my life. From editors and composers, and amazing directors … really beautiful, amazing people."

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While describing his evolving style as the new De'Longhi brand ambassador, Pitt told Esquire in September, "You get older, you get crankier, and comfort becomes more important. I think it's as simple as that."

Pitt's busy year also included joining longtime pal George Clooney in an upcoming thriller for Apple, launching a new champagne and announcing plans to reopen a legendary recording studio on the grounds of Chateau Miraval, his estate in the South of France.