SB is lagtag-ish, 39/26 but over a small sample...
HJ seems like a fish for calling here, but its the second hand i have on him 
BB is lagtaggy, not that good though...
is it ok to 3bet the river here? i was kinda surprised when he raised, couldnt really put him on a reasonable hand. 66 seemed the most logic, slowplayed KJ for some reason, 44 delayed, K6s... 75s 52s... i kinda had the last two in my mind but discarded em cause i couldnt se him calling with those in sb, not really K6s either...
PokerStars - $1/$2 (6 max) - Holdem - 6 players
Hand converted by PokerTracker 3
BB: $48.98
Hero (UTG): $29.01
MP: $145.66
CO: $92.65
BTN: $32.76
SB: $44.84
SB posts SB $0.50, BB posts BB $1.00
Pre Flop: ($1.50) Hero has K♣ K♥
Hero raises to $2.00, MP calls $2.00, fold, fold, SB calls $1.50, BB calls $1.00
Flop: ($8.00, 4 players) K♠ J♥ 3♠
SB checks, BB checks, Hero bets $1.00, fold, SB calls $1.00, BB calls $1.00
Turn: ($11.00, 3 players) 4♥
SB checks, BB checks, Hero bets $2.00, SB calls $2.00, BB calls $2.00
River: ($17.00, 3 players) 6♦
SB checks, BB checks, Hero bets $2.00, SB raises to $4.00, fold, Hero raises to $6.00, SB raises to $8.00, Hero calls $2.00
Spoiler
SB shows 5♠ 2♠ (Straight, Six High) (Pre 20%, Flop 26%, Turn 30%)Hero mucks K♣ K♥ (Three of a Kind, Kings) (Pre 80%, Flop 74%, Turn 70%)SB wins $32.20
what hands are in a calling range on sb with one cold caller in front? To me his play just seems awfully bad, is it, or is it ok to play this hand in sb under some circumstances?
is basically the only logical hand that has you beat. There might be some 57 combo but these are very unlikely. On the other hand He will definatelly raise any 2 pair here or better and these are quite a few. If he has 25 he for sure also have 36,J6,K6, then slightly less likely 66,KJ,33,44. You can clearly see that not 3betting here would be a big mistake.