If you decide to romance Firebrand in the end, after taking up your own hero persona or double as the Swashbuckler, the text makes him look very very clueless about who you are. Until you realize that he has proven to be very clever and a tease. He probably knows exactly who are (and by extension who the Swashbuckler is) and elects to keep it to himself, 'cause where'd be the fun in that?
There's a throwaway sentence when you are in the catacombs saying that you hear a sound down a path that sounds too large for a rat and not big enough for a sewergator just before you run into the mayor. In most endings, your twin has been held captive in the catacombs, so there's a chance it was them you heard. Extra points if the mayor turns out to be the M/Patriarch. Chance is they were not looking for you AT ALL.
In one possible ending, it might easily be that not only did you merge with your twin, but with the M/Patriarch, too, and they are still pulling strings without you being aware of it.
