I would like to know a few things.

Firstly, when you play a dynasty based faction, how you choose your faction heirs? Do you leave it as it is (the AI chooses brothers), or do you choose your own according to some houserules?

I prefer to keep a line, the heir is the eldest son. If the king has only daughters, he is chosen among kings brothers and sons-in-law as the most able. If the heir is going to be really crappy FM with bad traits, the heir becomes the most able from his brothers, uncles and brothers-in-law (brothers have higher priority). I tend to preserve the family name (like Syriakos or Baktrios).
By the most able I mean: highest influence, good traits or some deeds he has done before, like conquering an important region, victory in an important battle, governing capital or other important city.


Secondly I would like to ask how it was in reality, if being firstborn was important and how future kings were chosen (yeah, I know that in many cases knives played an important role when somebody thought that he would be a better king )