nuclear family

family unit (consisting of a father, a mother and their children); five nations that are known to possess nuclear weapons (United States, Russia, Britain, France, and China)

The term nuclear family developed in the western world to distinguish the family group consisting of parents (usually a father and mother) and their children, from what is known as an extended family. Nuclear families can be any size, as long as the family can support itself and there are only parents and children (or the family is an extended family.) According to Merriam-Webster the term dates back to 1947 and is therefore relatively new, although nuclear family structures themselves are not. Generally, the trend to shift from extended to nuclear family structures has been supported by the spread of western values. Today roughly one quarter of households in the United States, for example, are described as consisting of nuclear families, making them the third most common household arrangement in the nation.
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Noun
1. a family consisting of parents and their children and grandparents of a marital partner
(synonym) conjugal family
(hypernym) family, household, house, home, menage