KK -- how to sort out confusing action?

[fretelöo]

SB is an unknown. BB is 25/13/2 over 200 hands.

PokerStars 0.10/0.20 Hold'em (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is CO with K[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
UTG calls, <font color="#666666">4 folds</font>, <font color="#CC3333">Hero raises</font>, <font color="#666666">1 fold</font>, SB calls, BB calls, UTG calls.

Flop: (8 SB) J[img]/images/graemlins/spade.gif[/img], 7[img]/images/graemlins/diamond.gif[/img], 5[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">SB bets</font>, BB calls, UTG folds, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">SB 3-bets</font>, <font color="#CC3333">BB caps</font>, Hero calls, SB calls.

I had no idea what this meant. SB 3-betting didn't yet convince me fully that I was behind. BB call/capping was completely weird. someone trying to trap with 77/55? So I was pretty sure that I was behind BB and planned on folding the turn ui - which is in fact incorrect as even with SB calling, I only get 10:1 here. But anyway...

Turn: (10 BB) T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets</font>, BB calls, Hero calls.

... and he just calls. Huh? Since I originally wasn't convinced I was behind SB, I called as well. Correct?

River: (13 BB) 6[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets</font>, BB folds, Hero calls.

I really didn't like that 6, however after that kind of action, it was kinda hard to put anyone on 89s... So I made a crying call...

Final Pot: 15 BB

On a general note: That turn action somehow didn't make any sense. So what should I do in such a case? Scratch my previous ranges I put them on because they don't add up to their current play?
Go with what I thought on the flop and just assume they don't know how to play the nuts?
Not think anything anymore and just call down?