Dawnflight. The Dragon's Dove Chronicles, #1

What if King Arthur's queen was every bit as heroic as he was? Find out by immersing yourself in this epic story of the power couple whose courage and conviction would shape the destiny of a nation. Gyan is a Caledonian chieftainess by birth, a warrior and leader of warriors by training, and she is betrothed to Urien, a son of her clan's deadliest enemy, by right of Arthur the Pendragon's conquest of her people.  For the sake of peace, Gyan is willing to sacrifice everything...perhaps even her very life, if her foreboding about Urien proves true.
Roman by his father, Brytoni by his mother, and denied hereditary rulership of his mother's clan because of his mixed blood, Arthur has followed his father's path to become Dux Britanniarum, the Pendragon: supreme commander of the northern Brytoni army.  The Caledonians, Scots, Saxons, and Angles keep him too busy to dwell upon his loneliness...most of the time. When Gyan and Arthur meet, each recognize within the other their soul's mate.  The treaty has preserved Gyan's ancient right to marry any man, providing he is a Brytoni nobleman-but Arthur does not qualify.  And the ambitious Urien, Arthur's greatest political rival, shall not be so easily denied.  If Gyan and Arthur cannot prevent Urien from plunging the Caledonians and Brytons back into war, their love will be doomed to remain unfulfilled forever.
But there is an even greater threat looming. The Laird of the Scots wants their land and will kill all who stand in his way. Gyan, Arthur, and Urien must unite to defeat this merciless enemy who threatens everyone they hold dear.