Half a Secret - The Potter twins Book 1

Aurora Lily Potter. That was the name of Harry's twin. The twin who most nobody knew of, even him. While Harry grew up in the dark, not knowing he was a wizard, Aurora grew up at Hogwarts taken in by the teaching staff to become a very powerful young witch. However, when Harry comes to school his world get's flipped upside down as he discovers he had a sister.

All of this belongs to J.K. Rowling, the only things that belong to me are certain parts of the plot, MJ a few other characters that I have yet to make up and Aurora Potter :)