Ten years ago, nine children fled the war-torn planet Lorien and landed on Earth along with their adult teachers. The plan is to raise each child on earth until they develop their special powers called Legacies which help them fight the evil Mogadarians. The Nine children, protected and living on different continents can only be killed in order—and Number Three has just been murdered. That leaves Number Four: John Smith. At least, that's his latest alias, as he and his guardian, Henri, flee to another new town. John tries to lead a quiet life, but encounters bullies, falls in love, and begins to mature into his special powers.
If you like SciFi with an earthly spin, you'll like I am Number Four by Pittacus Lore.