Affiliation tags are a prefix (for instance [BEEZ] Queen4Lyfe) some players will add to their name to show that they are part of a certain group.
Given that Player 1's name is:
MainPlayer
Currently, if 2 (or more) players are playing on single device all other player's will be named:
At this time, this behavior is not configurable - but please do not suggest that this be changed. It's already planned and has been suggested endless times.