my sister and my reviles sister

What if harry wasn't the only one to survive? What if Lilly and Narcissa were friends in secret at school? What if Lilly asked Narcissa to hide her daughter away from the dark lord? How would this change Harry and Draco when Harry and Malfoy have to get along to keep her safe? What if she was the heir of Slytherin? What will Harry do when he finds out when the girl that was supposed to support was cheating out. Let's find out how the twins will get through this together and see what fate has in store for them