So he wanted to finish what his brother could not.

“We were supposed to be a team and someday run this marathon together,” Stephan told me Friday as he choked up. “Doing this by myself is probably the hardest thing I’ll ever have to do. But I just know I have to cross that finish line to honor him. I just have to do it.”

Stephan, the youngest of the eight Shay children, who all ran, was a college runner at Brigham Young University when Ryan died. Just like that, his close friend, his idol and his mentor, the brother who had helped him with training and with his career, was gone.

Stephan has fought through the tough times by remembering the good ones. Like the time after high school, in 2004, when Stephan spent a summer training with Ryan and other elite marathoners in Mammoth Lakes, Calif. He was just a kid brother, running with some of the world’s top athletes — including Meb Keflezighi and Deena Kastor — with Ryan as his guide. Between workouts, he and Ryan would go on what Stephan called mini-adventures, sometimes fishing for golden trout, other times exploring.

He said the best moment was when he and Ryan drove up a steep mountain they’d seen on their runs. As rain started to fall, their small pickup truck swayed on the slippery, windy road as Stephan begged Ryan to turn around.