How about you turn that around? Fyrgeiss is the owner and the Twins' father is the guildmaster? Much like how Lolorito owns Estheims, but is not its guildmaster.
Also, still not buying that Lolorito hired Nielle's assassin. Nielle was worth more to Lolorito alive than dead. The dude's mentality is a corporation, the very definition of being driven to profit, and Nielle's death would not be profitable. Trading the Garleans out of a war, on the other hand, would.
