Princess' suck. They start off with no charm and as you build them up the get nasty traits that bring them back down. If you marry them to an heir that faction is always the FIRST faction to declare war on me. And if not they are the second--right behind the other faction with a princess married into it.

The last good princess I had was in her thirties and I raced her from Russia to France where a family member was to marry him. Just as she got there my faction leader died and he became the next heir. So I couldn't marry her to him and I had to find another princess. grr.