should I fold this KK preflop 100bb

[cantsitstillbr]

UTG is 17/12 through 200ish hands
SB is 21/15 though 500ish hands

Both seem to play a tagish game, although UTG seems very unimaginative and SB seems to have more tricks up his sleeve, meaning I've seen him raise the flop in position with both a draw and a set.

Effective stacks of 100bb.

.25/.5 NL 6max

UTG raises $2. Hero make it $7 from the button with KK. SB lets his timer run about half way down and pushes(i know he plays multi-tables though so whatever). UTG lets his timer run down about half way and calls. Does hero ever fold this? If you say insta-call, at what size effective stacks does this call become a fold?

What about AK?
What about QQ?