What is the next clan to die, or be revived?

[Greifenstein]

I'm not quite sure, thought it was an unwritten rule.

Say if KH died, and eQ died, but I decided to bring back KH.

^ Not possible, or so I thought

Well, if you were a member of the clan when it died, there's no problem.
If you've quit the clan, joined another one, and that original clan died, it wouldn't look that good.