Half the fun is wrecking the realm.
I once had a king of Ireland who was literally perfect. Adrian the Just: smart, handsome, beloved, a valiant crusader...he died suddenly at the tender age of forty, and his idiot elder son proceeded to lose half of Ireland and fathered so many bastards I completely lost track of who was related to whom since he passed so many of them off. Oh, and one of his kids whom I shipped off to Norway to spread the dynasty somehow wound up getting blinded and castrated by the Byzantines. It took me two generations to recover from that disastrous king.
It was Haraldr Fair-Hair, First King of Norway and Emperor of Scandinavia for me.
It all started when his son and third in line to the throne, Baldur, asked him to let him go adventuring in the Varangian Guard. I said, sure, why not? It keeps him from plotting against his brothers and it's just the sort of thing us Vikings do, you know?
Then a plague took the firstborn. Then the second son lost his head as literally the only casualty of a minor war squashing a petty Jarl's rebellion. He was caught in an ambush. 
But Baldur had literally dropped off the face of the earth. I couldn't find him anywhere. Luckily I had some grandchildren, because the sons were all nearly as lustful as good king Haraldr.
But there were so many grandchilren and great-grandchildren. With gavelkind succession, the entire empire would be dismantled. (I'd kicked out the Christian missionaries a few weeks before the death and disappearances of the sons occurred within a week of each other. No primogeniture for me.
) So I started to panic. I issued a mass imprisonment and discreet execution of nearly all of my descendants, whittling it down to the finest of them all, Bjorn. Haraldr was 74 then, and in failing health. I figured he could take all the hatred long enough for his nicer great-grandson to take over.
Then Bjorn died, and Haraldr kept on living with that malus, fighting constant civil wars and assassination attempts. Since this was Haraldr Freaking Fair-Hair we're talking about, he crushed them all and sacrificed them to Odin.
As a hobby in his old age, he began to conquer bits of England and all of Iceland. He raided Italia. But still he needed an heir. He took up with numerous concubines, who kept producing ill children who died young.
Or worse, daughters!
Then one day a mysterious hobbled stranger returned home. It was Baldur!
Baldur, who had run afoul of the Byzantines. And by afoul, I mean he was blinded, castrated, maimed, rendered near catatonic from a blow to the head, heavily scarred, ugly, and had syphilis. I quietly set him up with an estate and presumably got him a dog to cheer him up.
Eventually one of the bastard daughters produced a fine, strapping man named Erik who became Emperor of Scandinavia when Haraldr Fair-Hair died at age 98.
Haraldr had imprisoned and slaughtered all of his vassals three times over by then, so everything was cool.
That was probably the most blood-soaked and kinslaying crazed dynasty I've had so far. But I've heard far worse tales on the forums.