Feudlings in Smoke (Fate on Fire #1.5)

Watching helplessly while your baby sister saves the world alone? It kinda sucks.
Will Delacour is one of the most powerful sorcerers to ever live. He’s Guard to the Edren Prodigy—his sister, Ari. But he walked away from the war, refusing to fight in a cause he didn’t believe in. He was deemed a traitor by the powerful Family, and now there’s a price on his head that leaves him trapped in a prison of his own making. And he can’t even tell the love of his life what she means to him because of the magical war that still controls their lives.
Instead of embracing his destiny, Will is forced to watch as Ari goes into battle over and over again, facing her enemies alone. She might be okay with it, but he’s not. He doesn’t believe in the war, but he does believe in her, and he knows his place is fighting by her side. Somehow, Will has to find a way to be there when Ari needs him , even if it means he forfeits his own life in the process.