Grandma and Grandson Who Overcame Estrangement Complete 7-Year Journey to Visit Every National Park

A grandmother and grandson who set out to visit 63 national parks have completed their quest after seven years.

Joy Ryan, 93, and her grandson Brad — who have amassed over 70,000 followers on the Grandma Joy's Road Trip Instagram page — finally made it to their last stop, the National Park of American Samoa in the South Pacific, on Monday.

"Reaching our 63rd and final U.S. National Park is bittersweet, with an emphasis on the 'sweet,'" Brad told Good Morning America.

"Standing at the finish line in American Samoa affirms that seemingly impossible goals are in fact possible if you pursue them with passion and pure intention," he added. "Grandma Joy has taught the world that you are never too old to show up and live the adventurous life of your dreams."

Getting to come along for the ride "has been the greatest privilege of my life," he said.

Joy was in her 80s when she and Brad first set out on their mission to visit every U.S. national park in 2015. At the time, she was working a minimum-wage job at a deli in Duncan Falls, Ohio, but craved more life experience.

PEOPLE spoke with the travel companions last September, where Brad detailed more of their relationship and how it blossomed.

"She had a huge, adventurous spirit, but never really had the means to do much in her life," Brad said at the time. "Her connection to the world was really through watching the Travel Channel."

Although they initially planned just to visit the Great Smoky Mountains in 2015, they had such a great time that they felt inspired to continue the journey.

"We got to the park around 1 in the morning, and it was pouring rain," Brad told PEOPLE. "She had never been in a tent before, but she held the umbrella over me and I put the tent together. We blew up the air mattress and she fell off a couple of times, but she laughed through every bit of it."

The next day, they climbed their first mountain together. "That's really when I started to realize that she was giving me just as much as she felt I was giving her," Brad said.

The adventurous pair started their journey after being estranged for "almost a decade" following the "ugly divorce" of Brad's parents.

Brad said he "felt betrayed equally as my mom felt betrayed," while his grandmother tried to support her son, Brad's father.

But after seeing him at his sister's wedding years later "pretty much needing to be carried in" he "felt horrible" for the distance that had grown between them. "Seeing her, I thought, 'Wow, this is going to be the guilt that I have to carry with me the rest of my life; that I stopped speaking to this grandmother who I was close to, and she's about to die,'" he said.

Fortunately, Joy's health recovered and the pair were able to "heal" their relationship.

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Thanks to their adventure of a lifetime, Joy said she had never felt more energetic, something their followers have picked up on as well.

"Every time I post a photograph, somebody comments, 'Is it just me, or does she look visibly younger than when you started when she was 85?'" Brad said. "And I don't think that's an optical illusion. I think that the experiences that we've had have literally unlocked the fountain of youth in her."

"He's taken me places that I see on the Travel Channel, and I never dreamt I'd end up there," added Joy. "It's been the most amazing journey."