Jinx's manga / #Full Color(3055)

Duke Rotary obsesses over which of his sons will be his heir, and the battle to succeed him is vicious. Born a boy, but raised as a girl by his mother to spare him a hard life, Crystal Rotary lives in peace until the Duke tries to marry him off. To protect his secret, he flees and offers himself to the rival Duke Illian Pentrin, hoping to hide there until he can escape for good. Little does he know he's not the only one with secrets.