The identification of extended family networks within multi-family households is of interest to many users of social statistics. The 'Relationship between families' variable, along with the 'Lone ancestor' indicator, can be used to identify the presence of 'extended families' in Australian families. In ordinary usage 'extended family' indicates a family comprising not only parents and children but also other members of the immediate family.

Data about the type of extended family within a household is gathered through the 'Relationship in household' questions. Of particular relevance to the 'Relationship between families' variable is the allocation of household and family reference persons. Relationships within families are assigned through the initial identification of a family reference person around whom the family is constructed. The familial or non-familial relationship which exists between families is established by examining the relationship between the reference persons of each family. For example, the reference person in the second family could be the son or daughter of the reference person of the 'Primary family'.

Another variable required to determine relationships between families is the 'Family number'. In multi-family households the families present are identified by allocating a different family number to each separate family.

The name of the variable is 'Relationship of non-primary family to primary family'. The standard abbreviated name is 'Relationship between families'.

The Census of Population and Housing provides output about such relationships and currently identifies up to three families in a household. In the 2011 Census the 'Relationship Between Families (RFLF)' variable was a family level variable that classified the relationship between the primary family and the second or third family enumerated in the same household. To identify the second and third families, the variable Family Number (FNOF) was required.

The relationship between families within a household is the relationship (familial or non-familial) of the second and any subsequent families to the primary family.

The relationship between families is measured by determining the relationship between the family reference person in a non-primary family to the family reference person in the primary family. The family reference person is determined by taking one person and then describing each other person's relationship to that person (see 'Discussion of conceptual issues' below). This allows the relationship between other members of the household to be identified and described.

The relationship is established by:

1. Identifying the families which exist in a household.
2. Identifying the family reference person in each family.
3. Identifying the family relationships of the second, third or subsequent family reference persons to the primary family reference person.
4. The relationship established by (c) then becomes the relationship of family 2, 3 or subsequent families to the primary family.

Relationship between families is an attribute of the counting unit 'family'.

NOTE: The number of families in a household is identified through the operationalisation of 'Family number', (see Glossary) which is a single-digit code assigned to each person to indicate to which family that person belongs.

The coding of a household member's relationship is based on the household relationship data collected in the 'Relationship in household' questions (see 'Relationship in household - Collection Methods'). The data, as originally collected, are dependent upon whom the respondent nominates as the household reference person. To achieve good quality data about family relationships, a standard is applied to ensure the accurate identification of the household or family reference person. If a respondent has nominated the wrong person, the correct person can be chosen by applying the standard hierarchical criteria as follows: 

• one of the partners in a registered or de facto marriage, or
• a lone parent, or
• the person with the highest income, or
• the owner, purchaser or primary rent payer of the household accommodation, or
• the eldest person.

Allocation of relationship codes in multi-family households is complex. Relationships in a household must be allocated on a family basis for each member of a family within the household. To facilitate this process, each family is separately identified by assigning a unique family number to each of its members. The 'Relationship in household' classification is then applied separately to each family in the household in turn (see the 'Relationship in household' standard and the Glossary).

Because the selection of household and family reference persons determine the relationships described, the types of relationships between families can be somewhat arbitrary depending on whom is selected. For example, in a household consisting of two cousins, their husbands and children, the category could either be 'Other related family' or 'Unrelated family' depending on whether the cousins or husbands are selected as the household reference person. The use of standard methods for selecting reference persons will alleviate (but not entirely solve) this problem (see Appendix A of the 'Relationship in household' standard).

The Census is the only collection which to date has published 'Relationship between families' data.

The criteria used to classify the relationship between families are: 

• whether the family is present in a multi-family household, and
• the type of relationship that one family reference person has to the family reference person of the primary family. The types of relationships that can be separately identified are immediate family, either vertically extended (parents, grandparents, children, grandchildren) or horizontally extended (brothers, sisters). More distant family members (e.g. aunt, uncle, cousin) will be grouped together into an 'Other related family'. If the family reference persons are not related to each other the relationship will be recorded as 'Unrelated family'.

The types of relationships that can be regarded as family relationships are described in 'Relationship in Household - Classification and Coding'.

The standard classification and code structure for 'Relationship between families' is:

This classification is only applicable to non-primary families in multi-family households.

'Relationship between families' is not applicable to any other variables.

The standard question module for this variable is the 'Relationship in household' question module (see 'Relationship in Household - Collection Methods').

The input categories are derived after: 

• each family in a multi-family household has been identified separately
• the family reference person for each family is identified
• the primary family is identified
• the family relationship between the reference person of the primary family and every other family is established.

The standard input categories for 'Relationship between families' are the same as for its standard classification and code structure (see the Classification and Coding page).

The standard output categories are the same as the standard input categories:

The following variables must be used to derive 'Relationship between families': 'Household/Family reference person', 'Relationship in household', and 'Family number'.

This variable is closely linked to the 'Relationship in household', 'Family number' and 'Household/Family reference person' classifications therefore any changes to these may have consequences for this standard.