It's In The Blood (Book 4). It's In The Blood, #4

The Thirst Within: SacrificeBook Four of the "It's In The Blood" SeriesTo save his grandfather's legacy, he must destroy his own family. The DeClue household is finally filled with the light of joy. As Macaulay and Dawndee prepare for a spectacular double wedding, hope for a peaceful future has never felt more real. But in the world of the Hybrid, darkness is never far behind-and on the night of the celebration, the family's beloved patriarch, David DeClue, vanishes without a trace.
While the search begins, an ancient, familiar evil is tightening its grip on the one person the family trusted most. Angel, the childlike vampire who has been their loyal protector for decades, is harboring a devastating secret. His connection to his grandfather-the monstrous Miguel Sanchez-runs deeper than the DeClues ever imagined. Now, the 18th-century killer has returned to demand a final, bloody sacrifice that will tear the family apart from within.
As newlyweds build their lives and outcasts like Lucifer and Tommy embrace their true nature, a traitor walks among them, sharing their home and their hearts. With the line between blood loyalty and cold-blooded betrayal blurred, the DeClues must face their most terrifying question yet: How do you kill an enemy you still love?