Hilton Israelson wanted to run a half-marathon on his 70th birthday. His children flew in from Brooklyn and Toronto to run the last three miles with him. But close friend and trainer Chas Briscoe has been getting him ready for the race since day one.

For Israelson’s 71st birthday, Briscoe showed up with five Bundt cakes.

“He just cracked up. He was like ‘What are you trying to do to me?’ and I said ‘I’m trying to keep my job,’” Briscoe says.

The job? Being best friends.

The two met because a friend of Israelson’s knew Briscoe. Israelson attended a session; ever since, they’ve spent the better part of three decades training, laughing and teasing each other. They play practical jokes. They enjoy a running bit about the raw sushi Israelson eats but that Briscoe won’t touch.

“They had this instant bond. They’ve always had lots of happy times and tragic times to sort of grieve together,” says Israelson’s daughter Alana Unterberg.

Briscoe’s mother, Perlie, died in West Texas. Israelson’s mother, Rose, died an hour later in South Africa. They were on the phone with each other within hours.

“We are talking many, many sessions of giving each other a hard time, loving each other, being there for each other,” Briscoe says.

“He’s just a constant, no matter what happens,” Unterberg says. “I unfortunately lost my husband two-and-a-half years ago, and talk about somebody to step up and be a role model for my kids,” she says. “They’re all — and my sisters’ [kids], too — are obsessed with Chas the superhero.”

Originally from South Africa, Israelson and his wife Maureen left the country to raise their children outside apartheid. The Israelson-Briscoe friendship goes beyond nationality, religion, race and age.

“We are all so alike. Doesn’t matter what we look like, what age we are. We all relate on a similar playing level. My eight-year-old and Chas have intense, learning conversations,” Unterberg says.

“If my dad has something funny to tell somebody, they always call each other, even if it’s a quick voicemail. My dad’s a 70-year-old white Jewish guy and Chas — he would kill me if I told you for real — but he’s a black gentleman from the South.” Unterberg’s advice is to be open to friendships of all kinds.

“I just want more people to see that, just like flowers, we are all just different colors,” Briscoe says. “But we are in the same in bouquet. We’re all in the same garden.”