To become a member of 2 great houses do this:
1. Join the great house Telvanni or Redoran (it is most important not to sign into house Hlaalu).
2. Get to Dren Plantation and find Orvas Dren.
3. Kill him (he's pretty strong).
4. Also, you must be a member of imperial legion with a high rank
5. Go to Ebonheart and find Vedam Dren.
6. Talk to him and he will ask you to tell his brother Orvas Dren that he is going to be named for new Guildmaster of house Hlaalu.
7. Tell him that his brother is dead and he will name you guildmaster of house Hlaalu.