Daughters of Darkness by L J Smith
The series takes place in a world similar to our own but one where vampires, witches, werewolves and shape-shifters live among humans without their knowledge. These supernatural races make up a secret society known as the Night World, which enforces two fundamental laws to prevent discovery: 1) Never allow humans to gain knowledge of the Night World's existence and, 2) Never fall in love with one of them. Mary-Lynnette, seventeen, loves to watch the stars from her Oregon backyard. Then one day, she thinks shes witnessed a murder through her telescope. Shes wrong: its only three vampire sisters burying their mysteriously-killed aunt. The sisters, Rowan, Kestral, and Jade ran away from their enclave home to live the lives of regular teenagers. However, when their brother Ash is sent to bring the girls back, he falls in love with Mary-Lynnette. But will she accept him because of his lurid vampire past and can a now-repentant Ash convince Mary-Lynnette to let him atone for his former sins and be his soulmate?
