Lay Me Down by Julie Mannino

In a single night, Remus Rizzo loses his Uncle Lupo, the position of Crown Prince of Rowland, and his freedom. Betrayed by his twin, he finds himself in the den of his bitterest enemy: the Crown Prince Sébastien Cadieux of Soleil.

To survive the lethal, icy Prince, Remus will have to step carefully. Thanks to the Rizzo’s actions, Sébastien lost everyone except for his Uncle Corentin, and the wrath under his pretty exterior has spent years boiling. Remus is his last chance for retribution.
To survive the court and a bigger enemy that wants them both dead, Remus will have to ally with Sébastien and find a middle ground. It doesn’t matter if Sébastien grows so angry at times that his eyes flash red or that some have sensed an odd energy about him. Neither can survive without the other.