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. The husband-wife example is called a sub-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.
Families are classed by type: married couple families (husband-wife families), Male headed family with no spouse present, or Female headed family with no husband present.
Families can have children present. These are usually called “own children” or “related children”. Own children are never married persons under age 18 that are son, daughter, stepchild or adopted child of the Head of the family. Related Children are own childred plus all other family members under 18 (regardless of marital status) related to the family head.
Group Quarters
All persons not living in households are classed as living in group quarters. Housing units occupied by 5 or more persons unrelated to the head in 1970, 9 or more persons in 1980, or 10 or more persons in 1990 were classed as group quarters. In addition, other living arrangements, such as college dorms and military barracks, are group quarters. Insitutions, such mental hospitals and prisions are called group quarters. Different census years did not define group quarters consistently, but this applies mainly to Types of Group Quarters.