When both players have the same 2 pair, can a 3rd pair be used as a valid kicker?
Player B wins. All that matters is the best 5 card hand you can make with the combined 7 cards. So player A does NOT have a pair of 4 as a kicker... player A has K,K,Q,Q,4. Player B has K,K,Q,Q,A. Both identical 2 pairs, but player B has A which beats 4.