0.50/1 Fixed-Limit Hold'em (6 handed)
Hand recorder used for this poker hand: Texas Grabem 1.9 by www.pokerstrategy.com.
Preflop: Hero is BB with K♥, Q♥
MP2 calls, MP3 raises, 2 folds, SB calls, Hero calls, MP2 calls.
3-bet?
Flop: (8.00 SB) T♣, A♥, 6♥ (4 players)
SB bets, Hero calls, 2 folds.
Turn: (5.00 BB) 5♦ (2 players)
SB bets, Hero calls.
raise turn as semi-bluff?
River: (7.00 BB) A♣ (2 players)
SB bets, Hero folds.
Final Pot: 8.00 BB
Without SB coldcalling in front of you you can 3-bet to knock MP2 out. But here you won't get HU.
If you are used to play big pot oop with many players then you can 3-bet here for equity value but be carefull postflop else you may lose more than you gain preflop. 
SB is playing a bit weird. I can't put him on a hand but he could donk a good hand because he fears a check behind. In this case a raise doesn't make any sense because he won't fold toppair or something like that.
I like the way you played it.
