In my Ireland game I had a king die early leaving behind a child who was, however, an uber-awesome genius. So one of the king's old cousins basically becomes the evil chancellor/vizier/regent and starts a war to lower crown authority, and succeeds, because he's evil™. So... the genius kid spends his entire childhood waiting the shadows, plotting his revenge, etc. etc. etc., and when he comes of age a new civil war breaks out, genius young king wins, evil chancellor imprisoned and dies, everybody lives happily after. And then this new genius, kind, just, awesome, great king dies of young age from depression, leaving behind another genius child king and a whole set of troubles.
That was fun.
Of course, this was all before I discovered how to have sibling incest via console command cheats.
Oh yeah! That reminds me of another Ireland story. So I had a pretty awesome king and wife, but for some reason for like the longest time I had only two kids, both girls. I really did not want to end up with a queen, just because of the vassal relationship penalty. Finally, getting close to 40, my wife gets pregnant. I eagerly wait for the kid, and huzzah, its a boy! Turns out though, he's got the imbecile trait. No way I was going to let that kid become king, with all 0's. So I had him killed before he even turned one. Next year, my wife got pregnant again. Another boy, another imbecile. I killed him too. Third year in a row, third imbecile in a row, third death in a row. I was growing hopeless, would I never get a boy who wasn't completely dumb? Then, fourth year, praise to the Irish heavens I finally got a boy who was normal, no traits or anything wrong with him. I pampered him, gave him everything he wanted, and I was getting ready to tutor him myself so that he may grow up to be just as great a king I was.
And then, on his fifth birthday, he dies. Not from natural causes either. He was murdered, by his older sister, who was now 22 years old. At that point my wife was well past 40, so I gave up and let her have the Kingdom for herself.
Turns out she was damn amazing. She ended up being the queen who conquered Scotland and created the dual crown throne. Who would have guessed?
This is the story I always tell my friends whenever I want to get them into CKII btw