After The I Do by Autumn Breeze

Necropolis, a city of mythical creatures, magic, and the occasional miracle, is host to a vicious power struggle between two prominent families.
The only solution is an alliance—an arranged marriage—uniting two men born to hate one another.
Thanos Right, the heir to the Moroii empire, agrees to wed Everett Dawson, the youngest son of the Vârcolac Clan, in place of his sister Sophia. A fragile trust builds between the young couple, but even as they explore their relationship the possibility of treachery is never far away.
In this high stakes game of love and hate, peace and war, loyalty and betrayal, Thanos and Everett will need more than a signed wedding certificate and an amicable introduction if they expect their marriage to end the centuries of bloodshed.
Sacrifices must be made on the altar of peace. The question isn’t when or what—but who?