Alpha Kings by Roe Horvat

As the king’s only omega son, Prince Aiken has been taught to obey in silence. Kept prisoner in his own home, his only destiny is to accept the alpha his father chooses and produce an heir to the throne.
Then one autumn day, barbarians defeat the king’s army and break into the castle: Aiken is taken hostage and brought to a citadel ruled by the formidable Cairistine lords. Suddenly, Aiken is allowed to look, speak, and roam on his own—and the things he witnesses are both outrageous and marvelous. How come the omegas at the citadel seem so happy? And who are the mysterious lords? What are they?
Bear and Wolf are the last of their kin, the true lords of Cairistine. Their powers have weakened, however, and unless a miracle happens, their sons will be born mere humans. While Bear has his doubts, Wolf believes in legends. If they can find the one omega who’ll give them twin sons from his first heat, the magic in their blood will be revived. None of this is on their minds when they kidnap Prince Aiken—they only want the war to end. But as time passes, the skittish virgin awakens desires in them both. They would never take an innocent omega against his will… but what if they seduce him?