To become GrandMaster of two Great Houses is really simple. First Join House Rederon or Tevalli become the Leader or GrandMaster of the House. In the Nerevarine Quest you have to kill Orvas Dren or make him step down to become Horator. After this happens talk to Duke Dren about Camonna Tong and he thanks you for controling them. You are now a Hireling of House Hlaalu. Talk to him again about Camonna Tong and he makes you a Councilman. Talk to him about business and he asks you th contol the ordinators, do this and your are the Grand Master. Note: This only works for House Hlaalu and one other Great House.