Ok, ok so I started a new game after the recent patch and it's going MUCH better than my Ireland game.
I've set up a perfect marriage and got my son to marry the princess of Castille whom was set to take over upon her fathers death. He died not long after and she took his spot and got her married to my son. I then made a election based government and got my son who was married to her to become the new King instead of his brother. I now have it where we have had a child and he is heirs to both my kingdom and HERS! It's fantastic. I'm playing as Barcelona and my Wife is Castile.
(Side note - Our relationship started out a bit rocky with her cheating on me, me promptly assassinating her lover and her trying to attempt to kill me but thats all in the past! Live and forget, we've gone through some counselling and were both over it and now have a happy loving family.)
(Side side note - Shes kind of a warmonger and I don't want to step on her toes so I try to tread lightly as she is very scary. She wears the pants around the house.)
Heres a screenshot of my game
I'm getting way into family simulator.