The Great Sunlight Silver Dragon had actually guessed a few things.
The ostensible reason back then was a difference in ideology, but in reality, it wanted to leave a bloodline within each faction of its family.
This way, the bloodline wouldn't risk extinction due to certain causes, as there were historically powerful bloodlines within the Dragon Clan that had ended for various reasons.
His daughter was strong-willed and liked to show off her bravery, so he had sent her to the Calamity Dragon Sea.
His son had been timid and lascivious from a young age, lacking ambition, so he had left him at Dragon Mountain.
He probably assumed the grandson in front of him was the seed his own son had sown outside, as he looked quite similar to him when he was young.
However...