RKCB

Asking about Kings 

We bid the King we hold. If we don't hold any, or if we hold a King above 6 in the suit, we bid 6 (suit or NT).

When holding 2 Kings, we bid the cheapest. Partner can bid 6 in the suit below trump, and this way asks about the King in the suit bid. Holding it, RE bids 6NT and partner choses the final contract.

When holding 3 Kings, we bid 6NT.