According to Shicoff, following the supernova that destoyed the Romulan homeworlds, the population split into three factions. The Tal Shiar is a dangerous sect led by Empress Sela that has no problems aligning itself with bad seeds. The Romulan Republic is a more peaceful group that seeks reunification and the end of xenophobia. And the final are survivors -- the players -- who are scattered everywhere and have yet to align with either of the two other factions.
Read up on the three factions over at Star Trek Online!