Boston Marathon Runners From Dracut Form Friendship Out Of Loss

BOSTON (CBS) -- Scott Middlemiss and Justin George are just two buddies, gearing up for their Boston Marathon Run.

Three years ago, these men were strangers. They were brought together by an amazing little boy who was lost too soon. But that little boy's impact lives on.

"I say it all the time, that I gained a lot from a six-year-old that I never even met," George says of Joseph Middlemiss.

Related: Father Crosses Marathon Finish Line With Son Who Needs Heart Transplant

Joseph was born with cardiomyopathy. He had an enlarged heart.

"He faced medical issues his whole life, but did it with a smile and kindness," Scott said of his late son.

Little brother Jack was just one month old when Joe's heart gave out in September 2013. Scott stayed at home with Jack while mom, Kate, went to the hospital with Joe.

George, a Dracut firefighter, was one of the first responders that day, and was leaving the hospital when he saw Kate sitting alone. He couldn't leave her there, by herself, so he stayed to console her.

"It wasn't even a thought. Someone was in pain and nobody was there," he explained.

"He saw someone grieving, saw someone hurting, and took the time to walk over, just to sit with me and keep me sane in those moments when I was alone," Kate recalls of that day. "In my eyes, he's a hero."

"He was there for us at the worst moment that any parent could experience," added Scott.

It was a simple act of kindness, one that was returned when George was deployed to Afghanistan. While he was gone, his family received weekly meals from a group organized by the Middlemiss family.

A friendship has grown from that heartbreaking loss. Together, these friends will run the 2017 Boston Marathon for Joe and The Big Heart Foundation, which bears the boy's name.

It encourages random acts of kindness, while also spreading awareness of childhood heart conditions and providing financial, social and emotional assistance to families impacted by them.

"Literally and figuratively, he had this enlarged heart that ultimately took his life. But he had this bigheartedness about him that really brought us life, and is bringing so much life and joy to others," Kate said of her son.

Jack is now three. He has the same condition that took his brother's life, and needs a heart transplant. Sister Grace -- who the Middlemisses call "an unexpected gift" -- is perfectly healthy.

They say Joe is always with them.

"If you keep your child's spirit and message with you, it will get you through anything," says Scott.

Even 26.2 miles.

Next Monday, Scott and Justin will be running together to help spread Joe's message. That is, if Scott can keep up.

"He's not very happy with my slow pace," Scott said.

But for George, any pace won't be a problem.

"I though of pushing myself, to challenge it and run at a certain pace," he said. "But the more I thought of Team Big Heart. If you're a team, that's what you're supposed to be doing."

To donate to George's Boston Marathon run, visit his fundraising page.