Vampire Academy

Trevor and Natalie were normal teenagers in a normal world. Notice I used "were" as in past tense. On Natalie's 13th birthday, she got a little surprise while brushing her teeth. Fangs. That's right, fangs. Her father promised he will explain everything as soon as Trevor also turns 13. Until then, wear fake teeth he says. Wait 3 years to know why you have fangs, he says. On Trevor's 13th birthday, your mother isn't dead but is living in another magical dimension as the world's most powerful being who is seeking for your help because you two are the only ones who can save this world from utter chaos, he says.

"Oh, by the way, we're vampires."