Brother from a Box by Evan Kuhlman
Matt Rambeau is officially a big brother--to a robot! Matt's super-computer-genius dad is always getting cool tech stuff in the mail, but the latest box Matt opens contains the most impressive thing he's ever seen: a bionically modified lifeform that looks human and calls Matt "brother" (in French)!
Norman turns out to be a bit of an attention hog and a showoff, but Matt's still psyched to have a robotic sibling--even if he flirts with (ugh) girls. Then strange things start to happen. First a computer worm causes Norman to go berserk, and then odd men start showing up in unusual places. Matt soon realizes that someone is trying to steal the robot--correction--his brother!
In this zany, action-packed story with spies, skateboards, and plenty of artificial intelligence, acclaimed author Evan Kuhlman gets to the heart (and motherboard) of one of the most special relationships known to man (or machine): brotherhood.