Eddie Hunter is Shawn's half-brother who lives at the Pink Flamingo Trailer Park introduced in The Pink Flamingo Kid. He's resentful of Shawn's situation when he lives with Mr. Turner, and believes that Shawn will eventually end up slumming the the trailer park again, just like him and the rest of his family.
Eddie is also involved in theft. He's caught on tape with a stolen laptop, which inspires Cory to investigate the story and enter it in a news contest that Mr. Williams had told him about. He catches Eddie with stolen stereos then, but Eddie sees him and destroys the tape. Shawn interferes in the issue just in time, and Eddie goes off. Instead of using the tape (which he had saved), Cory gives it to Shawn.
Eddie also has a sidekick, an 11-year-old named Danny, who terrifies Cory.
Eddie is never seen or heard from again, so his existence is considered a continuity error.
As it's never specified on which half Eddie is Shawn's brother, it's entirely possible he's not even a Hunter as he's never actually referred to with this last name. Many fans speculate that Eddie is in fact Virna's son from a previous relationship, so as to explain his far more minor role in the series as Virna is rarely around.
Eddie could be chet's son from a previous relationship because Chet was married 62 times and Eddie looks like chet more than virna.