Twenty-six years have passed for legendary football coach Tom Coughlin. There have been Super Bowl championships on the field — and the joys of becoming a grandfather off of it. But the sadness of watching Jay McGillis die has never left his heart.

McGillis was a redshirt freshman on the 1991 Boston College Eagles team who immediately became one of Coughlin’s favorite players. Quiet but fearless, the Brockton, Massachusetts, native was “the All-American boy,” Coughlin, 72, tells PEOPLE.

“An overachiever. A great teammate. Guys loved and respected him,” says the famously hard-driving coach, who went on to coach the Jacksonville Jaguars and New York Giants, and is now an executive with the Jaguars.

That November, McGillis was the starting strong safety when Boston College was set to play Miami, the top team in the nation. But days before the game, the team’s doctors told Coughlin that McGillis couldn’t play: He had swollen glands and was running a fever.

The news got worse quickly when Coughlin learned McGillis had leukemia. The disease was “ravaging,” says Coughlin, and eight months later, having lost 75 pounds and his signature red hair, McGillis died at 21.

Watching McGillis die was devastating — and so was watching the athlete’s family sit a daily vigil at the hospital. He never forgot the emotional and financial toll those months took on the middle-class family, and Coughlin vowed that if he were ever in a position to help such families, he would.

In 1996, while coach of the Jaguars, he launched The Tom Coughlin Jay Fund, a support organization for families with children battling cancer. The organization has raised more than $10 million and touched more than 5,000 families.

“When you tell a family their child has cancer, their world is turned upside-down,” says Coughlin. “The child knows the parents are stressed — he just senses it. So the idea is that the parents are not alone and you’re helping them — it might be mortgage payments, utilities, food, car payments. Once the parents know there’s someone that will help them, they can then relax and let the child know that what’s important is for them to beat the disease. That’s the role we play.”

Coughlin says the months he spent watching McGillis die gave him perspective, reminding him that despite the long hours of game film study being a football coach requires, it isn’t a life or death matter. To his players, his devastation at McGillis’s death showed that under the gruff, intense exterior was a human being who cared.

He formed a close bond with the McGillis family that persists to this day. When McGillis was sick, Coughlin’s players set about gathering donations from the surrounding community from people who would pledge money for players “max-out” weight-lifts. The team raised more than $50,000 for the McGillis family and during their spring intra-squad game, they presented a check to them.

At McGillis’s memorial service several months later, his teammates packed into the chapel. “There wasn’t a dry eye in the place,” says Coughlin — including his own.

‘His Life Is Not in Vain’

The Jay Fund is active in the New York metropolitan area and in northern Florida, places where Coughlin became a local football hero. Celebrated players from those teams — including Michael Strahan and Eli Manning — have helped the charity.

A typical activity is the Sundae Blitz event, during which pediatric cancer patients come to the training facility of Coughlin’s teams and do football drills with players before capping off the day with ice cream sundaes.

“There’s a tremendous sacrifice for these families, and it’s a day off from cancer,” says Coughlin. “The parents can enjoy it because they see their child having a good time.”

September is Childhood Cancer Awareness Month, and to mark the occasion, Coughlin teamed up with former Vice President Joe Biden and Dr. Jill Biden as well as the Grammy-winning rock band Imagine Dragons to film a public service announcement, which will run on television outlets and at sporting venues.

According to the CDC, approximately 15,000 people under the age of 20 are diagnosed with cancer each year, or about 43 a day.

Joe Biden’s son Beau was 46 when he died of brain cancer in 2015, leading to the launch of the Biden Cancer Initiative. The Imagine Dragons launched the Tyler Robinson Foundation to combat childhood cancer when a 17-year-old fan, Tyler Robinson, died of cancer in 2013.

Each of these charities began with the inspirational story of one individual. This is McGillis’ lasting legacy, says Coughlin.

“Jay died young, but his life is not in vain,” he says. “He has over 5,000 families who he has helped. All these people know his name and know why they were helped. And that means a lot to me.”