Complex Family is a generic term for any family structure involving more than two adults. The term can refer to any extended family or to a polygamy of any type. It is often used to refer to the group marriage form of polygamy.
A joint family is also known as a complex family, parents and their children's families often live under a single roof. This type of family often includes multiple generations in the family. In India, the family is a patriarchal society, with the sons' families often staying in the same house.
In the joint family setup the workload is equally shared among the members. The women folk are often housewives and cook for the entire family. The patriarch of the family (often the oldest male member) lays down the rules and arbitrates disputes. Other senior members of the household baby sit infants in case their mother is working. They are also responsible in teaching the younger children their mother tongue, manners and etiquette.
The house often has a large reception area and a common kitchen. Each family has their own bedroom. The members of the household also look after each other in case a member is ill.
This kind of setup is fast eroding in many parts of the world especially in India. Most of the urban families are switching over to the nuclear family society these days.