Weak play?

[Charon]

1/2 game, 6 handed.

UTG+1 (extremely aggressive player) calls, button calls, I in the SB call with As6s and BB checks.

Flop 3c 3s 5s

Checked to the button who bets, I check-raise, all call except button.

Turn is the Kd

I check, BB bets, UTG+1 calls as do I.

River is the Ks

I check, BB bets, UTG+1 raises and I fold.

Standard? Fishy?

[Schneids]

Sounds ok to me.

Having two people cold call 2-bets on a paired board usually means at least one of them has trips.

You may occasionally run into the time when BB has A5 and UTG+1 has a smaller flush but I think that's rare.