Blood of the Innocents — Jennifer St. Clair

Ten years ago, Orien, crown prince of the Seleighe, was captured by his mortal enemies, locked in a dungeon and turned into a vampire. Six years into Orien's sentence, the Healer's brother Cullen disobeyed his mistress's orders to kill him and turned him into a vampire instead, thus sealing both their fates for all eternity.

Now both Orien and Cullen are set free. But a secret only Cullen knows lies locked inside his mind, threatening to drive him mad before he can uncover the identity of a traitor--the very elf who betrayed Orien and left them both to die in darkness.