Family number (FNOF)

Latest release
Census of Population and Housing: Census dictionary
Reference period


This variable categorises multiple families in a household as either the primary, second or third family. Families in a one family household are always classified as the primary family.


Families in family households


1Primary family
2Second family
3Third family
@Not applicable

Number of categories: 4

Not applicable (@) category comprises:

  • Non-family/Non-classifiable households
  • Unoccupied private dwellings
  • Non-private dwellings
  • Migratory, off-shore and shipping SA1s

Question(s) from the Census form

What is the person’s relationship to Person 1/Person 2?

How this variable is created

This variable is derived from the Relationship in household question on the Census form.

In a multiple family household, a maximum of three families can be identified. In cases where more than three families are identified in a household, the first three families are coded. The other persons are classified as either related family members of the primary family or non-family members.

Where there is more than one family in a household on Census Night, the family with dependent children is designated as the primary family. If there was more than one family, and no children were present in the household, then the first family identified on the Census form becomes the primary family.

History and changes

This variable was first introduced in 1971, to replace the previously used Family group (FMGF) variable. The mnemonic used has changed several times.

No changes have been made for 2021.

Data use considerations

The maximum of three families in a household may have only a small effect on the total number of families overall. However, the impact may be more significant among population groups who are more likely to live in multi-generational households or with large numbers of extended family members.

The term 'Primary family' is an ABS term that is used to aid coding of household relationships. This should not be misinterpreted as signifying that this is the main family in the household or the family that owns the house or for any other reason, other than for ABS relationship coding purposes.

This variable does not have a non-response rate as it is created during Census processing by using responses from one or more questions on the Census form.

Related variables and glossary terms

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