Odds of set-over-set on flop?

If you are dealt a pocket-pair in holdem, the odds of you flopping a set or better are 7.5/1.

What are the odds of another player also flopping a set? My first thought was that it would be (7.5*7.5)/1 or 56/1 but I think it's actually smaller than that since there are only 2 cards left to make the set (although there are different combinations of ways the 2 sets can be made)

Also, I realize this can be a more complicated problem, since there are the odds of another player having a pocket pair to begin with, and then the odds of that player also hitting a set on the flop.

Odds of one player getting set:
50 unknown cards, 2 make the set
odds of not making set: 48/50 * 47/49 * 46/48
odds of making set is 1 - above = .118 or 1/8.5

Forgetting the odds of getting the pocket pairs preflop, assuming two players see the flop and both have pocket pairs, how would you compute the odds of them BOTH hitting sets?