Lover Avenged by J.R. Ward

Rehvenge has always kept his distance from the Brotherhood—even though his sister is married to a member, for he harbors a deadly secret that could make him a huge liability in their war against the lessers. As plots within and outside of the Brotherhood threaten to reveal the truth about Rehvenge, he turns to the only source of light in his darkening world, Ehlena, a vampire untouched by the corruption that has its hold on him—and the only thing standing between him and eternal destruction.