The Celestia Trilogy by Nicola Zhang

Sixteen-year-old Prince Anden has no memory of the night his father died. People say he caused the accident; his brother the king has never forgiven him. Now exiled in disgrace, Anden receives a mysterious note. “You didn’t slip. You were pushed. Your father didn’t drown. He was murdered.” Anden falls for charming palace squire River, but the timing couldn’t be worse. He returns home to find his kingdom surrounded by enemies, his brother about to come of age, and their uncle the Lord Regent making moves to usurp the throne. Anden must race to uncover a decades-old conspiracy before it destroys his kingdom, his family, and the boy he loves. An epic coming-of-age fantasy trilogy with a slow-burn gay romance at its heart, set in a rich medieval-inspired world with no overt magic. Complete series!