First Guardian and Last Line of Defense: Year 1

AU, rewrite of Alliances series, Slytherin!Harry, eventual HPDM. Harry's twin brother Andrew is the Boy-Who-Lived, and he is devoted to protecting him by making himself look ordinary, while Andrew is made to look like a hero. But there are certain people not content to let Harry hide in the shadows, and one who is set on convincing Harry that he is more than what he thinks he is.