BOSTON (CBS) – The heart and soul of the Boston Marathon are the people who run, cheer and volunteer. Race director Dave McGillivray has run Boston 46 times. But this year is different.

Boston Marathon race director Dave McGillivray. (WBZ-TV)

It’s his first marathon after major surgery. And he’s dedicating it to a special five year-old. Jack Middlemiss is a non-stop inspiration for McGillivray.

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“He’s always positive. He’s always inspiring. Motivating. He’s just a ball of fire,” McGillivray says of Middlemiss.

Jack Middlemiss. (WBZ-TV)

Sixteen months ago Jack, who has cardiomyopathy, had a heart transplant. Joe Middlemiss, Jack’s older brother, died of the same disease when he was just six

Their parents, Scott and Kate, created the Joseph Middlemiss Big Heart Foundation to encourage kindness, support education, fund research and help other families. Their marathon team is 13 runners strong.

Race director Dave McGillivray has run Boston 46 times. But this year is different.

“It makes us so proud and happy that his legacy lives on,” Scott said.

Scott ran the Boston Marathon three times for the foundation. His finish in 2016 with Jack gave us all something to celebrate when he crossed the finish line with Jack.

Scott and Jack Middlemiss cross the finish line in 2016. (WBZ-TV)

“This platform, the greatest race in the world, allows us to make sure that more and more people know about our son and remember how wonderful he was,” he said.

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McGillivray was already behind the “Big Heart” mission when his own heart began failing. He had triple-bypass surgery last fall.

“I thought, ‘Talk about the stars lining up.’ Now’s the time to dedicate this marathon to their foundation and, in particular, my buddy Jack,” McGillivray said. “Every time I feel frustrated about what I’m experiencing, I think about what he went through.”

Jack Middlemiss and Dave McGillivray. (WBZ-TV)

Jack and Dave have a bond that’s formed over years at races and celebrations – and now as survivors.

”It’s beautiful to see how they connect with one another,” Scott said.

On Monday as one warrior battles the course, the other will wait at the finish line. Each will be representing what makes the Boston Marathon more than just a race.

“It’s about the pursuit of athletic excellence. But we also have an event that’s changing and saving lives. It doesn’t, it can’t get any better than that,” McGillivray said.

McGillivray’s raising awareness about heart disease and raising money for the Big Heart Foundation with his run. His goal is to raise $100,000. So far he’s at $99,000. He says that’s the fundraising equivalent of making the turn onto Boylston — with the finish line, he hopes, in sight.

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For more information on the Joseph Middlemiss Big Heart Foundation, visit their website.

Lisa Hughes