Harry Potter Heir to the Founders (Book 1)

When Voldemort attacks the Potters, the killing curse rebound's upon him as he tries to kill Harry.His twin sister Rose is thought to be the girl-who-lived and Harry is sent to Dursleys, but Dumbledore makes the mistake of leaving him on the doorstep so Merlin, who knows what Harry will have to suffer brings him to the time Hogwarts was built so he can raise Harry with the founders