Josh is Krusty's nephew. His last name has not been revealed.
History
He has red hair that bears a striking resemblance in shape to Krusty's green hairdo. It is possible that Josh is the son of Krusty's sister, whose existence is implied when Krusty throttles Sideshow Mel for seeing his sister.[1] When Homer is briefly famous for Police Cops, Krusty takes a picture of Josh kicking Homer.
