Currently, the Mother has total control over the Haus! This includes designing the look of the Haus, promoting and demoting Sisters, accepting/rejecting join requests, and removing (already accepted) players from the Haus.
The Co-Mother helps the Mother accept/reject requests to join the Haus, and can be promoted to Mother if the original Mother decides she needs to sashay away!
The Sisters are all of the members of the Haus! They may be promoted to the Co-Mother, if the Mother so chooses.