An extended family is a family that extends beyond the nuclear family, consisting of parents like father, mother, and their children, aunts, uncles, and cousins, all living nearby or in the same household. An example is a married couple that lives with either the husband or the wife's parents. The family changes from immediate household to extended household.
A nuclear family, elementary family or conjugal family is a family group consisting of two parents and their children (one or more). It is in contrast to a single-parent family, to the larger extended family, and to a family with more than two parents.
Over the past 20 years single-parent families have become even more common than the so-called "nuclear family" consisting of a mother, father and children. Today we see all sorts of single parent families: headed by mothers, headed by fathers, headed by a grandparent raising their grandchildren.