Garth Brooks and Trisha Yearwood Are 'Not Surprised' Pal Jimmy Carter Is 100: 'Money Is Always on' Him (Exclusive)

Garth Brooks and Trisha Yearwood are honoring their friend Jimmy Carter’s 100th birthday by getting their hands dirty. 

The pair — who first met the former president and his wife Rosalynn Carter through their shared participation in Habitat for Humanity building projects — spent Jimmy’s milestone birthday on Oct. 1 in St. Paul, Minnesota for the 2024 Jimmy & Rosalynn Carter Work Week Project, building the first 30 of what is going to be a 1,200 home community.

“There was an eagle that flew over the site yesterday for the opening ceremonies, and we all thought ‘That's Ms. Rosalynn putting her blessing on this place’,” Yearwood, 60, tells PEOPLE about Rosalynn, who died last November. She adds about Jimmy, who is currently in hospice care, “He definitely wants to know that we're working and this is why we're here. He has a legacy of service and he never stopped serving. He's not physically standing here building, swinging a hammer, but we feel his presence and Ms. Rosalynn’s presence strongly. We're just two volunteers, but everybody who's on this site feels that responsibility to make them proud."

Speaking on his and Yearwood’s special relationship with the Carters, Brooks, 62, says it was how “regular” the former president and first lady were that bonded them. "Their family, their work ethic, that was something that I loved immediately,” Brooks says. “His sons are out there working their asses off and Ms. Rosalynn did not back off of anything. She might've been the hardest-working one of the whole bunch."

The CEO of Habitat for Humanity, Jonathan Reckford, recalls meeting the Carters during his final interview nearly 20 years ago. “They sat holding hands in a little double rocking chair and just couldn't have been kinder. And I think for them it's always about that faith in action. And I think they've often been asked, ‘Why didn't you retire? Put your feet up.’ And they just were sort of stunned by the questions. ‘What kind of life would that be? There are things to do and people that need help.'"

Brooks and Yearwood learned valuable lessons in service and work ethics from the Carters, but their greatest lessons were about love.

“Just working with them, one of the greatest lessons you learned was that it's OK to argue,” Brooks tells PEOPLE. “They would argue about how to build or do something, but it just brought them closer. So my favorite thing about getting to be Ms. Yearwood’s partner is the good times, but also going through the bad times together because that makes you one… we have a love that's going to last beyond this lifetime. I found her in the last life. I'll find her in the next one.”

Yearwood adds about their relationship, “And at the end of the day, we're best friends. We actually enjoy each other's company. I can't imagine doing this build without [him]. I mean, we are a team and I think that’s definitely something we have learned from the Carters. They were a team.”

While many are surprised to see the former president make it to 100 years old, Brooks and Yearwood say they don’t find it that surprising. “My money's always on President Carter,” Yearwood says. “I remember being in Haiti and he's 90 and he's talking about what he is going to do in the next 20 years. I am not surprised!"

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Brooks adds, “We all bet that he was going to be around a long time and he has not let any of us down or disappointed any of us. The fact that he was there for Ms. Rosalynn's funeral was very touching and the fact that he still remains among us is because he knows she's fine. It's us that needs the help.”