BOSTON (CBS) -- The Boston Marathon is not just a showcase of some of the world's best runners, but also about our family, friends and neighbors.
And most importantly, the very personal reasons they run.
Scott Middlemiss of Dracut is one of those people. He is running in Monday's 119th Boston Marathon, because his sons can't.
"He was my best friend and I miss him a lot," Scott says of his son Joseph. "He was six but he was wise beyond his years. He taught us a lot."
Joseph Middlemiss was a little boy with a very big smile, and an even bigger heart -- in every sense. He was born with cardiomyopathy, an enlarged heart.
"It made his heart work harder," Scott explains. "It put a strain on his body. It made it hard for him to do things boys like to do."
But Joe was too busy enjoying his life to worry about what he couldn't do. He loved music and superheroes, and he loved to go to school with his dad, who is the associate principal at Tyngsborough Elementary School, where Joe went to school.
"He really had a gift of finding the best in every single day and making the most of it," Kate Middlemiss said of her son.
"Every day Kate would ask him how his day was," remembers Scott, "And he would say, no matter what, this was the best day ever."
One of Joe's very best days came when baby brother Jack was born. But barely a month later, Joe was gone.
"He was so excited to be a big brother," said Scott. "They did get some time together, but not enough."
"The 33 days we had together were bittersweet," said Kate. "But they were the best days."
Scott and Kate's focus is now on Jack, but they are working hard to keep Joe's spirit alive.
They started the All You Need Is Love Mission, which strives to honor Joseph's memory by "spreading his love, kindness and compassion."
"We have mission cards. It tells Joe's story and asks people to do an act of kindness and pass the cards along," said Scott.
Those cards have reached all over the United States as well as Australia and England. That led to The Joseph Middlemiss Big Heart Foundation, and a second mission for Scott and Kate.
"The second goal is to teach children the importance and impact of kindness," explained Scott.
"We use the word 'Ripple Kindness' -- do something kind and how it ripples out to the entire community and the world," said Kate.
The foundation is also funding research to find a cure. Like his big brother, Jack also has cardiomyopathy, and is on the list for a transplant.
A cross country runner in high school, Scott returned to running as kind of a therapy after losing Joe.
"It always came back to 'Why don't you start running?' It'll be good for your physical health and your emotional health," said Scott.
"I know he is holding Joe close to his heart in every mile he's running," added Kate.
And Joe will be with him when he makes that 26.2 mile journey from Hopkinton to Boston next Monday.
"I know he's inspired Scott to make the Boston Marathon the best day ever," said Kate.
"It will be such an accomplishment, something that I've worked hard for," said Scott. "And just know that Joe and Jack were with me the whole time, and carrying them in my heart -- that'll be great."
The Joseph Middlemess Big Heart Foundation also provides support for children who are hospitalized and their families, as well as giving out scholarships for music and martial arts -- two of Joe's favorite things.
Stay tuned for more coverage of the 119th Boston Marathon on CBSBoston.com and WBZ-TV — the exclusive local broadcast home of the Boston Marathon!
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