This is George Finklestien - or 'Geo', as he prefers to be called - Maggie's younger brother.
He may be a bit of a bully, but he really is a sweet person deep down. He loves his sister more then anything - and therefore hates Jeremy. In fact, when Jeremy and Geo first meet, the kid just walks up to Jeremy and kicks him in the balls. How's that for protecting your siblings? =P