Gaia Rising by C.L. Roman
If she loses, she dies, but winning will break her heart. As second in line to the Black Throne, Gaia expected to live her life in the shadow of her brother, Lukas, as he followed the requirements of the Wushe treaty and married a princess from another clan to maintain the balance of power among the Simoi. But when Lukas is murdered, Gaia is thrust into the role of heir. Her new responsibilities include a marriage of political convenience to the power hungry, arrogant prince of the Hingani clan, Atoli, despite her growing attraction to his brother, Bardan. Multiple attacks on Gaia’s family make it clear that someone doesn't approve of the marriage, and they’re willing to kill to prevent it. With the fate of the entire Simoi race at stake, Gaia must fight through secret enemies and cold-blooded assassins in order to save herself and her people from annihilation. This dynamic space opera introduces a new species to the cosmos - the Simoi, sentient planets with god-like powers and deadly enemies.