Communion Blood

British Fantasy Society: Best Novel nominee (1999).

Olivia Atta Clemens, Saint-Germain's love from the days of Imperial Rome, has died the True Death and left her lavish estates to her servant, Niklos Aurilios, but they have been claimed by a young noble who says he is the long-lost son of Olivia's dead husband. Saint-Germain may not be able to convince a court of Niklos's rights without revealing Olivia's true nature, and therefore, his own.