That's how I lost a pretty good king, the grandfather of the current guy.

"The door to your bedroom chamber suddenly opens..." and BAM! dead. And I am fairly sure it must have been his wife. Somehow. Couldn't prove it.
The father of the current kinslayer+realm duress king got the event "Is that a dagger in my back?" which only has a 33% of survival. Of course he died too.

I could see that it was his bastard son (whom he had made a prince!!!!) because he got the kinslayer trait following this dynastic changeover.
The current king got the kinslayer trait after taking revenge for his father... first he stripped the rebelling bastard brother of all his titles, then once he had fled to some far away court he had him murdered. Sweet revenge.

Except for being branded as a kinslayer of course.
It has been... difficult... since then. First the queen mum rebelled, whom I had given land and titles. I let her go because all her stuff will fall back to me anyhow. Then the whole court, except for some loyal guys, packed up and left. And now I am postponing my plans of grand conquest again and again. Because either my armies desert or the vassals rebel.
I only have those two or three loyal courtiers to lead armies, the rest will cause the dreaded "Disaster - there is treason in the air" event within a month of being given an army. I tried to sail an army to Tunis once, 16000 men, and forgot to check the loyalty of the courtiers. Of course they rebelled once they got through the Bosporus. And I don't want to send my king out to battle until his sons are old enough to rule should he die.
Sucky sucky, let me tell you! Otherwise the realm is in damn good shape: King of Rus and Finnland, all the juicy provinces in Russia are in my demesne, lots of prince vassals, 90% of them loyal despite the sucky traits of the king. And because there is a war going on in the Byzzie empire, I get new refugees every month. They start out at 100% loyalty so for some time I can use the guys as advisors... until they plummet to 0% loyalty, too...

o
In my last game I once got an event "Character thinks about faith" where if you choose the first option, you can get rid of all kinds of bad traits like kinslayer, cruel, deceitful, indulgent, proud, and so on, at 10% odds each. I got rid of kinslayer that way.

Unbelievable luck!! (I had the king murder a distant relative previously.) Unfortunately my current king is sceptical so I guess he's never going to see that event. GRRRRR!!!!