To personal trainer Sammy Callari, 13-year-old Parker Seward is more than a client. He's his "little bro."
Over the past year, the pair from Naples, Florida, have bonded. They play basketball together, share meals and dance to hip-hop like no one's watching.
"Everything just clicked from day one," Callari told CBS News.
The trainer was asked to work with the 13-year-old, who has, while his coworker was out of town last spring. Callari had never worked with someone with a disability before. He was anxious the first day he met Parker.
But Parker's big grin and cheery introduction immediately put him at ease.
He reminded Callari of himself when he was a teenager. Like Parker, Callari has also faced his fair share of challenges over the years.
"The cards have always been against him. Society has always been against him," Callari said. "We're underdogs."
As a high schooler, Callari described himself as being the skinny, scrawny kid. When it came to sports, he was always overlooked. His dream of playing baseball in college quickly faded away.
"I had a chip on my shoulder," he said.
When he went to college, Callari turned to a new sport. His younger brother trained him to become a mixed martial artist.
Callari participated in five matches. Out of four of those fights he was the underdog, and he won three times.
"I know how it feels," Callari said. "Society tells you 'you can't do this, you can't do that.'"
When it comes to Parker, Callari refuses to accept the word "can't."
The friends meet twice a week to train. They bike, box, run and work on their core with push-ups and planks. Parker has a short attention span, so it's Callari's job to keep him focused.
"I'm centered on him," Callari said. "I don't want him to go through life thinking he's going to get a pass."
Callari shares videos of himself and Parker working out and goofing off — with Parker's mom's permission, of course.
It's clear, Callari says, that Parker is an inspiration.
"If Parker can do it, if he's having fun, even with his setbacks, then people will ask, 'Why can't I do that?'" Callari said. "That's the whole mission right now."
Callari recalls Parker's mom once thanking him for taking a "chance" on her son. Callari told her he never viewed it that way.
Parker may be the student, but Callari says he's the one who's learning.
"He's made me a better trainer, but he's also made me a better person," Callari said. "A lot of people see him as different, but I've never looked at him like he has Down syndrome. If anyone's different, it's me."