Hand converted with online PokerStrategy.com hand converter:
$0.5/$1 Fixed-Limit Hold'em (6 handed)
Preflop: Hero is MP2 with K:s, K:d.
Hero raises, 2 folds, BU calls, 2 folds.
Flop: (5.5 SB) 3:d, 3:s, 6:c (2 players)
Hero bets, BU calls.
Turn: (3.75 BB) T:d (2 players)
Hero bets, BU calls.
River: (5.75 BB) 5:c (2 players)
Hero bets, BU raises, Hero calls.
Final Pot: 9.75 BB.
Can I 3-bet this? I think no, because his raise is either a bluff or a 3.