How does one get princesses?

[Nestor]

The manual says (yes, I read it) that they are members of the royal family not just the daughters of the king. And yes, I've never seen them in the game playing with the Byzantines.

Please ppl don't give advice like RTM if you don't know all the facts.

In another campaign as Scotland I did find them in the agent page, with the Byzantines I don't. It may be faction specific, it may be something else, but the problem is real! Now, I have princesses in the family tree but not on the campaign map.