Shadows in the Dark: Rise of Three

Veronica Michelson and Zach Turner learn that they aren't normal teenagers by another teenager just like them, Jennifer. They are half-vampires, a very rare species. These three teenagers are part of six. The most powerful of their kind, and they must find the others and fight demons that try to kill them. Not every one likes the presence of a new type of vampire. Love emerges. Hearts break. And friends die. This three book series all begins with three.

(I get the ideas of this book from Cassandra Clare's Mortal Instruments series, The Vampire Diaries, Lorien Legacies by Pittacus Lore, along with other countless supernatural books and movies.)