His Beast Returns — Erin M. Leaf

Tristan Marik fell in love when he was too young to understand that he wasn't allowed happiness, particularly not with another boy. As the son of Edmond Marik, ruthless owner of Monolith Enterprises, he had an image to maintain. After his father threatened his boyfriend's life, Tristan spent years pretending he'd never sworn a blood oath. But now, everything has changed.

Russell Kelvin dreamed of the day he'd return to Tristan because he thought it would happen on his terms. He thought they'd be free to love. Instead, his ability to call his beast is the only thing that can keep Tristan alive when enemies want him dead.

Fear keeps Tristan from fully trusting Russell's intentions. Instinct keeps Russell by Tristan's side, even in the face of doubt. But oaths made in blood never fade, and the drive of the beast is stronger than either of them realize.