S. M. Stirling - Shadowspawn (#1-3)

A Taint in the Blood (Shadowspawn #1)
Eons ago, Homo Lupens ruled the earth. Possessing extraordinary powers, they were the source of all of the myths and legends of the uncanny. And though their numbers have been greatly reduced, they exist still- though not as purebreds.
Adrian Breze is one such being. Wealthy and reclusive, he is more Shadowspawn than human. But he rebelled against his own kind, choosing to live as an ordinary man. Now, to save humanity, he must battle the dark forces of the world-including those in his own blood...

The Council of Shadows (Shadowspawn #2)
Adrian Breze defied his own dark heritage as a near-purebred Shadowspawn for years, until his power-hungry sister Adrienne kidnapped his human lover Ellen.
Now, Adrienne is dead, and the Council of Shadows is gathering its strength. To stop the Council from launching an apocalypse, Adrian and Ellen must ally with the Brotherhood, a resistance group dedicated to breaking the Council's hold on humankind...by any means necessary.
In the coming confrontation, Adrian must fight not only the members of the Council but also his own nature-and, as he will come to suspect, traitors within the Brotherhood itself...

Shadows of Falling Night (Shadowspawn, #3)
She’s back....
Near-purebred home nocturnus Adrian Brézé and his human mate, Ellen, thought they had dealt with his twin sister, Adrienne. In fact, they thought she was dead. But she survived and now leads a faction of the Shadowspawn—the ancient, shape-shifting, blood-drinking breed who secretly control the world—that wants to leave just enough of the human race alive to satisfy their hunger and serve their needs. She has nothing but hatred and contempt for her brother, who remains on the side of humanity, fighting with the Brotherhood against the Shadowspawn. To defeat him, she has suborned his mentor—the greatest warrior of the Brotherhood. The man thinks he’s bringing a weapon to the Council of Shadows that will wipe out the Shadowspawn’s leaders. In truth, his actions will make Adrienne demon-goddess of the world...unless Adrian and Ellen can turn him back in time.