Authors Note: This story is based on Harry Potter and Buffy the Vampire Slayer. But I am rewriting the timeline and other things. So almost everythings different from the books and tv show.
"Of Potters and Blacks"
Prologue
On July 31, 1983 Elizabeth Anne Black was born to Sirius Black and Joyce 'Snape' Black. Remus Lupin and Lily 'Evans' Potter was named her godparents. Her uncles and aunts were 'Uncle' Severus, 'Uncle' Remus, 'Uncle' James, and 'Aunt' Lily.
On Elizabeth's "Buffy" 3rd birthday (1986) Harry James Potter was born to Lily and James Potter. (He was born on July 31, 1986.)
On October 31, 1987 Elizabeth, Harry, James, and Lily was at home when Voldemort attacked their house. (James, Sirius, Lily, Joyce, Harry, Elizabeth and Remus all live together at Godric Hollow. They all are under the Fidelius Charm. Because Dumbledore thought that Voldemort was after Harry. Peter Pettigrew was the secret keeper but everyone thought that Sirius was.) He killed James and Lily. When he raised his want to kill Elizabeth he told Elizabeth and Harry that he wasn't after Harry but he was after Elizabeth. But when he raised his wand to kill Elizabeth the spell rebounded off of her and hit him in the chest and made him into nothing but a soul. Both Elizabeth and Harry were hurt by the spell. Elizabeth got a cut shaped like a phoenix on her back, across both of her shoulder blades. And Harry got a cut of a lightening bolt in the middle of his forehead.
Sirius went after Peter after he learned what happened. Peter started to yell that Sirius was the secret Keeper and the he betrayed James and Lily. Then he blew up the street full of muggles and cut off his finger and transformed into a rat and ran down the sewers.
Since everyone believed that Sirius was the secret keeper and that he was a death eater and gave the Potters to Voldemort, the Ministry sent him to Azkaban Prison without a trial for life.
Joyce divorced Sirius and took Elizabeth to California. She oblivated Elizabeth and got remarried to Hank Summers and oblivated him too
to make him think he was Elizabeth's father. Then she spelled Elizabeth's hair to the color blond. Then left the magic world forever.
But what she didn't know was that Elizabeth remembered everything about her real father and that Hank wasn't her father and what happened on Halloween. She never called Hank dad or father ever.
Everybody thought that Harry was the one to defeat Voldemort that they gave him the name the Boy-Who-Lived! But boy were they wrong.
Dumbledore let Sirius get sent to Azkaban, when he knew he was innocent, then he took Harry and left him on Lily's sister's doorstep to live through years of abuse and neglect.