All persons occupying a single housing unit are referred to as a household . All persons who are not members of a household are regarded as living in group quarters. Persons per household , single person households, two person households, etc. refer to persons in households and exclude group quarters.
Families are two or more persons, living in a household, related by blood, marriage or adoption.
All persons living in a household related to each other are regarded as one family. For example, a son of the head and the wife of the son living in the household are treated as part of the head s family. Sub-families are not included in the count of families as there can be only one family per household. The definition of family has not changed over the course of the 1970-1990 censuses, but some documentation for 1970 indicates that married couple families living with relatives are counted as families Not all households include families. Unrelated individuals can live within households with families.