Flicker by Jamie Baddorf

Breeanna never quite fit in with the rest of her family, especially her “twin” brother. His blond hair, blue eyes, and athletic physique clashed with her freckled, stocky frame. Unfortunately, all her questions regarding the circumstances surrounding her birth were met with stony silence.

Suddenly a handsome stranger appears in town, and his interest in Breeanna is something far beyond that of any normal teenage boy. Bree is about to find out that her true identity lies at the center of a war that has been waging halfway across the world for over five centuries.