Kingdom of Feathers by Deborah Grace White

A prince who’s king too soon, a princess determined never to be queen—two kingdoms at war

Princess Wren is not the crown princess. Everyone else might think her six older brothers are dead, but she knows the truth. They’re very much alive, and her oldest brother will absolutely assume the throne. Once he becomes a little less feathered…and beaky. The trouble is, that requires Wren to fulfill the terms of the curse that transformed her brothers into swans—which means she can’t speak a word to a living soul.
For six years.
Prince Basil wants to become king at eighteen about as much as he wants to inherit the war that’s burdened his kingdom for six long years. With the death of his father, he’s determined to ignore all advice and reach out to their enemies for an armistice. Even if there’s no one to negotiate with except the kingdom’s silent, timid crown princess. After all, there must be more to her than meets the eye…otherwise the dragons Basil regards as friends wouldn’t take such an interest in her.
But other forces are at work, ones with no desire to see the war end. If Wren and Basil want to save their people from further loss, they’ll have to learn to trust each other. Because the only way to uncover their true enemies might be to embrace the ones they thought they knew.