Topic: So, in order for two people to play X and Y...

do they have to have the same version? (example: a person with X can only play against other people who have X)

No of course not.

Nope, X & Y are totally compatible with each other! In fact, it's a good idea to communicate with the other version; they'll have Pokémon that aren't available (i.e.: Pokémon available in X might not be in Y and vice versa)!