The Sacrifice (Legends of Transylvania series #1)

Two young children named Alexander and Ariana are inseparable until their parents are killed in a car crash and their lives fall apart. Having lost contact with each other, they meet again 13 years later when they fall in love, and become embroiled in a bitter feud between vampire and other supernatural factions. Curses cast upon them cause Alexander to become a vampire and Ariana to become a wild jaguar, which threaten their very existence. Will they find a way to break the curses and gain their salvation?