Religious/Tribal Clans Demographics:
Most of Yemen is Sunni. There are very strong Salafi/Wahhabi influences from Saudi Arabia, in addition to strong conservative tribal traditions. There are some Shia, and they live alongside Sunnis. Sectarianism is not a primary problem in Yemen.
Tribes are a major deal in Yemen, particularly in the north. Tribal regions are ruled by local and regional sheiks, as well as by loose tribal confederations. Tribes are very highly armed, and do not act monolithically, even within individual tribes.
There are Yemenis of African descent, who have darker skin than the Arab Yemenis, and are treated as second-class citizens. They are most often street-cleaners, maids, and garbage men.