Rules on imprisonment

[Mr. Charisma22]

I know that when you are fighting a war, and you capture the enemy king/duke/etc, he is released after the war ends. What about the family of the enemy ruler that you can capture after the siege of his capital? Are they sent back after the war, so should I ransom them before the war ends or can I wait?

 

[RforRush]

You know, there's wiki about this game.

Prisoners will also be released if the captor chooses to:
Sign a peace treaty, if the prisoner contributes to the warscore (100% for ruler, 50% for spouse or heir, 5% for ruler's other children)