The Hall of the Mountain King - Avaryan Rising, #1

The king's heir of Ianon is long lost, vanished into the south. Her father refuses to name his son heir in her place, though that son is a mighty warrior. Then one day a young wanderer arrives with news that both breaks and heals the king's heart: his heir is dead, but before she died, she gave birth to a son. That child, now grown, has come to take her place. But the king's son will not surrender his hope of kingship to a boy without a father, though he claims to be the son of a god.