The son of a retired NYPD sergeant whose brave battle with cancer inspired a “Sesame Street” character passed away at his home this week, relatives said.

Danny Mulvey, 20, who was diagnosed with leukemia at age 4, was the basis for a heart-warming muppet named Chester, whom Elmo visits in a hospital bed.

Danny was the son of former Sgt. Daniel Mulvey, who served the Upper West Side’s 20th Precinct.

In 2001, Danny got a bone-marrow transplant, but the leukemia returned three years later, according to his family.

He spent some of the year in a hospital bed — at a time when coverage of 9/11 and its aftermath were often on TV — and developed an admiration for the US armed forces, they said.

Last month, Danny was named an honorary solider at a touching ceremony at a firehouse in Chester in Orange County. An Army general swore in Mulvey who, despite being wheelchair-bound, insisted on standing for the oath.

The Sesame Street clip featuring the character Danny inspired shows Elmo singing a song titled “Here for You.” Chester is Elmo’s cousin.

“A nice man told Elmo laughing would make Chester feel better,” Elmo says in clip, which is part of a “Sesame Street” resource video shown to sick children.

“He was right,” replies Chester, an adorable orange muppet.

Danny Mulvey is also survived by his mother Maureen and sister Alicia.

A viewing for Danny will be held Saturday and Sunday from 4 to 8 p.m. at Flynn Funeral & Cremation in Monroe, NY.

His funeral will be held from Monday at 11 a.m. at St. Columba Church in Chester.