Showing An Old Friend of the Family by Fred Saberhagen

Dr Emile Corday, aka Dracula, is summoned to the aid of the Sutherland family, descendants of his great love, Mina Harker. Corday finds himself facing a rebellious faction of American vampires out to see him and anyone he cares for annihilated. Leading his adversaries is the evil and alluring enchantress Morgan Le Fay.
Corday, the Sutherland family, and the policeman Joe Koegh will cross paths in seven more books of Saberhagen’s Dracula series.