Gabrielle Black is left in an orphanage when her father goes to Azkaban. One day she gets an unexpected guest who tells her she's a witch and she's been accepted to Hogwarts. Once there, she befriends Fred and George Weasley and they get in a lot of trouble together. (This is a rewrite of an old story, own nothing but my OC & rated T for possible future chapters)
Gabrielle Black, Sirius Black's daughter - shocker - is left in an orphanage. When she is eleven, she gets an unexpected guest, bringing her the news that she's, in fact, a witch. She leaves her life behind to go to Hogwarts School Of Witchcraft And Wizardry, where she befriends Fred and George Weasley. Starting two years before the Harry Potter books.
What happened at Hogwarts while Ron, Hermoine and Harry were on their horcrux-hunt? How will Ginny, Neville, Luna and Seamus survive in a school taken over by Death Eaters? *disclaimer: i do not own harry potter of course*