What's the best way to annihiliate an enemy's family?

I was playing with William the Bastard, and after conquering England, i stumbled upon the problem of how to deal with the remaining Godwinsons(a few of them died in battle). So i just granted them bishoprics, apart from Harold himself, whom i kept as a prisoner at first, then castrated and plotted to revoke his titles.

A few decades later, the Duchess of Aquitaine decided to demand my installment upon the throne of France, declared war for my cause, i joined with her and before long i was also King of France. Same story again - i had some very powerful vassals i wanted to get rid off, and since the game doesn't permit you to go all Rains of Castamere on an enemy's family, i resorted to the same policy - giving a bishopric to any male i could find, and plotting to usurp titles/insult vassals so that they start plotting/declare war and i have a claim and can easily usurp their titles.

That generally works, but it's:

1. Slow, i need to build a lot of temples
2. Costly, #1
3. I have a gazillion bishops who somewhat like me(because of land grant), but are from families i don't want to be around. Currently the best candidates for Chancellor, Spymaster and Court Chaplain are bishops from either the Godwinson or Capet families. And there are even one or two of them who became Cardinals.

So, here's my question in essence - is there any good way to destroy a family without incurring significant tyranny? I can hope to imprison all characters from a family, and execute/castrate/blind most of them, but everybody else will hate me(which is wrong, a Norman Duke in Jerusalem shouldn't care that a French Count of Champagne and his family were obliterated).

If they were my courtiers, i could also marry them to whomever i want(like old, sterile, lowborn people in the middle of nowhere), and order them to take the vows, but that's not always an option.