JJ facing weird action on the turn and river

UTG+1 is 29/12/1,0 over 800 hands

Party Poker 0.50/1.00 Hold'em <font color="#0000FF">(10 handed)</font> link

Preflop: Hero is MP2 with J[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/spade.gif[/img].
UTG calls, UTG+1 calls, <font color="#666666">1 folds</font>, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">MP3 3-bets</font>, <font color="#666666">4 folds</font>, UTG calls, UTG+1 calls, <font color="#CC3333">Hero caps</font>, MP3 calls, UTG calls, UTG+1 calls.

Nothing to discuss right?

Flop: (17.50 SB) 9[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/spade.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">UTG bets</font>, UTG+1 calls, <font color="#CC3333">Hero raises</font>, MP3 calls, UTG calls, UTG+1 calls.

Not a dangerous flop at all, couldn't have wanted a better one (except for two JJ's [img]/images/graemlins/tongue.gif[/img] )MP3 who showed strenght preflop is now just cold calling. I wonder what UTG have here though that bet/calls

Turn: (12.75 BB) 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
UTG checks, <font color="#CC3333">UTG+1 bets</font>, <font color="#CC3333">Hero raises</font>, MP3 folds, UTG folds, <font color="#CC3333">UTG+1 3-bets</font>, <font color="#CC3333">Hero caps</font>, UTG+1 calls.

All of a sudden UTG+1 wakes up. Did that five make him a set? Or can he have 66's playing his OESD this hard? How do you guys like my line here? Call down his bet? Call down his 3-bet or cap it?

River: (20.75 BB) 9[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
UTG+1 checks, Hero checks.

Huh? I probably missed a bet here but I'm lost what to do

Final Pot: 20.75 BB.