A Blaze in the Dark by Miranda Turner

Bain never thought he’d escape the prison he’d lived in for the last five years. He spent his days chained up like an animal, and his nights…they were better not spoken about. Until one day Antonio came stumbling into his darkness, lighting a fire in his soul and giving him a chance at a new life.
Antonio loved his position as a Bellator, and he loved his brother Luc; it was Luc’s friends he could do without. When he came upon an emaciated and beaten boy at his brother’s best friend David’s house, he knew he had to get him out of there. Risking his place on his team, his relationship with his brother, and even death was something he’d never regret. After all, Bain was Antonio’s sodalis vitae, and soulmates were forever.
The small problem of Bain being a member of the Tenebrix, the Bellators’ mortal enemies, was nothing compared to what could happen if David found out where he was. But Antonio won’t let anything—race, being hunted by his own kind, or Bain’s fears—keep him from finally claiming his mate on Valentine’s Day.