The Knight — Pierre Pevel

This novel charts a dynastic power struggle between three brothers. When the King dies his will, to everyone's surprise, leaves the throne to the second of his three sons. It's a surprising choice, and a worrying one as it coincides with a prophecy: that the succession will lead to war, chaos, and the undoing of the entire nation. It's something his eldest son can't allow to happen - so he challenges his brother's right to rule, as does the youngest son, with the full support of the Church behind him.