I am playing my first game in EU IV as Castile and it is pretty awesome. However, I got dragged into a personal union under Austria and I am wondering how this could have been prevented. I had four Royal Merriages but I didn't get a heir. When my monarch died, I found myself as a vassal of Austria.
Thus, I have two major questions:
How can I actively prevent getting dragged into a pu ahead of time? What else can you do than establish Royal Merriages? Is there anything else?
Now that I am a vassal, how to deal with it? What can I do to make the best out of my situation? Are there any other options than fighting a war to become independent again? If I fight such a war, who will be the new leader (since there is no heir)?