Villain 1 on the button here is big fish and very passive, villain 2 in the big blind has more or less just sat down and I have no information on him, never come across him before:

UTG ($27.38)
UTG+1 ($55.29)
MP1 ($20)
MP2- Hero ($20)
MP3 ($43)
CO ($23)
BTN ($11.60)
SB ($20)
BB ($25.83)

Hero is dealt Ks Kc
Pre flop ($0.30)
utg calls $0.20, 2 folds, hero raises to $1, 2 folds, btn calls, sb folds, bb calls, utg calls

Flop ($3.90) is 9d 5d 3s
bb check, utg check, hero bets $3.60, btn calls, bb raises to $24.83 and is all in, utg folds, hero?

My thoughts here are the bb has a set, what else is he raising with here? What are your thoughts?