I started a game as Leon last night. Right off, muslim attack. Castille had done a bit to piss me off in the first few months but I'd already joined in on their side to fight off the invaders. Slowly managed to retake all of my counties for myself. Married early to a young princess of Navarra, although my first child was a bastard daughter that I legitimized. Wife wasn't too happy as she was also pregnant and gave birth just a few weeks later.
Castille ended up losing the war against the muslims without losing much land in the process. I took the chance to strike while she was weak, taking her land easily even having to fend of Aragon, Navarra, and Galicia. Mercenaries helped and while I cut it pretty close budget wise, I ended up finishing the war before anything major happened. Couple more daughters, one more bastard daughter to a different mother(Wife of a count in the former Castille area). (Wife ended up plot killing the first mistress.)
Galicia's king dies, leaving it to his daughter. I start a plot to kill her off while also looking around. So far, my sister is dead, by Galicia brother is dead, my Castillian brother is reduced to a lowly duke. He hates me already and it doesn't take long for him to rebel. I crush him easily and imprison him. Realizing my fortune I execute him. Yeah, kinslayer and all that, but with that, I'm the last of the family... other than my mother. Once Galicia's young queen is dead, it defaults back to my extremely elderly mother. She's not happy with me obviously, but hell, she dies a couple of years later, in the middle of a war, giving me about half a Galicia, the other half to muslim occupiers. Navarra(Wife ran back there after I caught her trying to kill ME) and Aragon are pissed, pissed enough they won't even help me against the Muslims anymore.
So currently I'm nearly broke and fighting an army of muslims 3 times as big as anything I can muster without mercenaries.
This will take some thought, if I can even survive it. My daughter(s) might have better luck, it's hard to say.