KK vs AA preflop

[NoPepperJack]

In the past four days, I have been blessed with KK preflop four times.(Texas Holdem) Twice in a 3-6 game, twice in a NL Tournament.
I have been beaten 3 of the four times. In the three six game the opponent called me down with a small pair and caught the second pair with the river card. Later in the same game, same guy had AA to my KK preflop and I called him down. NL Tourn, I catch KK and it holds up, twenty or so hands later, I catch KK and go all in against what turns out to be AA. I lose again....

Probability question (I have no idea how to calculate this, am just real curious)

What is the chance that you will be against AA when you have KK? I would be real surprized if it is 50%!

Thanks for your help.

Jack
NoPepperJack