99 UTG, call or fold river donk?

[cdxx]

the villain just sat down, so no reads. 3/6 party

Hero raises, 3 fold, SB calls, BB 3-bets, Hero calls, SB calls. (9 small bets, 3 players)

flop, 4x6x4h. check, check, bet, call, call.

turn, Qh. check, check, bet, fold, call. (8 big bets, 2 players)

river, Kh. BB bets, Hero ...?

i doubt very much he 3-bet PF with anything other than AK, AQ, KQ. i can rule out any pocket pairs.