Billy Fuentes is the young son of deceased Marine Larry Fuentes and housewife Rosemarie Fuentes. He seemed distraught and grief-stricken at the news of his father's death. It was later revealed that prior to his murder, Fuentes had been helping his young son build a tree house but after Fuentes's death, Billy seemed to accept that it would never be finished because his father was dead. Luckily, Special Agent Leroy Jethro Gibbs, having caught Larry Fuentes's murderer arrived at the house next morning and helped Billy finish the tree work much to Billy's joy.