AU. Harry's little sister: Emma Lily Potter, most witches and wizards don't know she exists. How different would he be growing up with a someone he loved and who loved him back? Harry and Emma go to Hogwarts where they make friends, duel, brew illegal potions, form a guild, fight Wizarding prejudices and get burdened with a terrible secret. Now with Elemental Magic. H/G E/C R/H N/L