(This is the sixth in a series of previews on local Boston Marathon participants)Bob Catinazzo of Saugus runs the Boston Marathon to benefit Children’s Hospital, and each time he does it (this year will be No. 3), he gets to meet the child his fundraising assists.”They pair me,” Catinazzo said of the hospital’s Miles for Miracles program.This year, he is running for a 2-year-old boy from Lynn, A.J. Sorrentino, who has a congenital heart defect.”He’s a beautiful little boy,” Catinazzo said, “a brave little boy. I know his family personally.”Catinazzo described A.J. and his parents as personal friends of his.”It’s pretty amazing,” Catinazzo said. “If you don’t know a patient, they pair you with someone through Miles for Miracles. My first two years I (ran for) a little girl with leukemia who I knew personally.”This year, she is healthy.”They have amazing technology at Children’s Hospital,” Catinazzo said. “It’s very humbling, a pretty humbling place.”What led Catinazzo to run for Children’s was in part his own work with youth in Saugus. The Revere native and Dom Savio graduate (Class of ’85) is now the president of Saugus National Little League.”I’m very involved in the community with kids,” said Catinazzo, who is a father himself (he and his wife, Caroline, have a son, 10-year-old Cameron). “There’s nothing more heartbreaking than seeing a sick kid. Anyone will have a story about Children’s Hospital. It’s a pretty amazing place. Running a marathon is nothing. I run 26.2 miles one day ? these kids run 26.2 miles every day.”Catinazzo had a relative who died of complications in her 40s several years ago, who was born without kidney functions. She was a patient at Children’s in the 1970s.”They pretty much kept her alive,” he said, adding that otherwise, “I don’t believe she would have made it to her 40s.”Catinazzo’s charitable efforts, and the marathon running that generated them, sprang from a Red Sox game on Patriots’ Day a few years back. He and Cameron were participating in a time-honored tradition – a father taking his son to his first-ever Sox game – with a friend and his daughter. After the game, he saw marathon runners still going through Kenmore Square, and he told his friend that next year, he would run.”He said, ‘You’re crazy,'” Catinazzo recalled. “But I could see the runners’ camaraderie and support.”When he crosses mile 26.2 this Patriots’ Day, it will give him his fifth major race completion (3 Boston Marathons, a Disney World Marathon and a Disney Half-Marathon).His preferred everyday running venue is his neighborhood in Saugus, in the Lynnhurst section, and he makes good use of the advice that “a real good runner” once gave him: “Run out your door.”That he does, at 5 a.m., being on the lookout for traffic all the way.”Everyone’s been fabulous,” he said. “They understand what I do. The last three years, what I like is that people keep supporting me. I’ll keep running as long as I’m healthy.”This year, he will have friends cheering him on at mile 13 ? and his wife and son, as well as A.J., his parents and brother, all at mile 25.”I have a real good support team,” Catinazzo said. “There’s nothing like seeing my wife and son at mile 25.”