The Other Doppelganger

Hannah Stilinski is Stiles Stilinski's twin sister. After Claudia Gilbert died, Hannah had to go live with friends of Claudia's, Grayson and Miranda Gilbert. Hannah grows up with Elena and Jeremy. At school she is known as Hannah Gilbert Elena's twin because Elena and Hannah look identical. When Grayson and Miranda die in a car crash Elena, Hannah and Jeremy go live with Grayson's sister Jenna Sommers. Hannah video calls Stiles daily but she won't talk to her dad. When she meets the Salvatore brothers she gets roped into the supernatural. When Katherine Peirce comes into Mystic Falls she turns Hannah into a vampire. Hannah is more like Katherine than Elena. (Skipping a few seasons for description) When Jeremy gets killed by Katherine Peirce, Elena and Hannah both turn their humanity off. Though Elena only killed one person, Hannah killed a lot of innocent people due to her uncontrollable thirst. When Bonnie resurrects Jeremy Hannah turns her humanity back on, consumed with guilt Hannah leaves Mystic Falls and goes to Beacon Hills...where her brother is...

Disclaimer: None of the character are mine except Hannah.