The Inner Sun Domain has a structure like the Outer Sun Domain, and the only difference was there had a fourth region, the Private Sector Region.
The Private Sector Region was quite big, and it was divided into private territories which could be claimed by any High Union Elder Rank Cultivator.
Not only that, those High Union Elders then could decide to let their descendant live there and races related to them as long as they were willing.
Furthermore, a High Union Elder has another interesting authority. They could get married in the Moon Domain to any woman they wanted as long as she was one rank below them. They could even marry High Union Elder Rank Women in the Moon domain as long as they were willing and had descendants.
Not only that, but High Union Elder of both sides could choose a hundred men or women to be part of their private sectors, and then those women or men could marry those people who were allowed to live in the private sector.