Krystal or Volga will have to contact them for a compromise.
This happened to be back when I lead SotN and I just talked to the other clan leader, and we worked it out. I pretty much had rights to the name because I had a topic and had the acronym before he did.
I'm guessing their KC stands for KWorld's Clan. Maybe you can have them spell clan with a 'k', so it would be KK as their acronym. Either way, it should be fixed before any confusion or arguments breaks out in-game.
Edit:
It seems now that KC has been somewhat successful, I've noticed more clans that are having categories and such like we have.
It's kinda annoying, no one is specializing anymore, they're just copying us. :\