"I've gotten to know his family over the years and they're just amazing," the actor, 37, told PEOPLE Saturday at The Michael J. Fox Foundation for Parkinson's Research Benefit in New York. "They're just an incredible lot of people."
"We have that connection – we're all from the same part of the world," he added, referring to their mutual upbringing in Vancouver, British Columbia.
Another attribute he and Fox have in common? A shared mission.
PEOPLE's former Sexiest Man Alive first teamed up with Fox, 52, in the fight against Parkinson's disease – which Reynolds's father also suffers from – five years ago when he ran the ING New York City Marathon, as the first celebrity chair of the foundation's fundraising arm Team Fox. Since then, the two actors have grown closer.
"He's incredible in everything that he does, from the foundation to his work to his work ethic," Reynolds says of the star of the new The Michael J. Fox Show, which marks the actor's first starring television role in 13 years. "There's a reason why everyone likes this guy so much – he's just unsinkable."
As for his own father, Reynolds is grateful for the support Fox's foundation provides.
"My dad's hanging in there," he shares. "Like so many people who are afflicted with this disease, they have an incredible resource in this foundation ... They also have a reason for hope."