What is the sociological definition of a family?

Functional definitions of families are more inclusive

Question: What is the sociological definition of a family?
Position‹4 of 6›: Families are defined by what they do
Argument1 of 5›: Functional definitions of families are more inclusive

By defining families by what they do rather than what they are, we can include all the modern variations of a family unit in the sociological definition of a family.

The argument

But allowing any unit that performs the core functions of a family unit to be classified as a family, the functional definition can be more inclusive. It means foster parents, that may not be legally or biologically related (or may not even be living under the same roof any longer) can still be classified as a family. It means people who did not form bonds with their biological parents or grandparents, but found a new “family” that provided support and shared resources have also entered a new family, as it provides all the functions of a family. It also means that whoever provides care for frail or elderly “family” members, whether they are biologically related, lifelong friends, or close companions, can meet the functional definition for a family.

Context

Limiting families to only those related by blood, those living in a shared accommodation, or those which raise children, are exclusive definitions of family which fail to accommodate all the nuanced family setups of the modern world.

Premises

[P1]A family can be defined by the core functions it performs—care, support, and shared resources—rather than by biological or legal ties. [P2] A functional definition includes foster parents, chosen families, and caregivers who perform these roles regardless of blood or legal status. [P3] Biological and legal definitions exclude many units that genuinely fulfill these family functions. [C] Therefore, families are best defined by what they do, since a functional definition is more inclusive of the units that actually serve as families.

Counter-arguments

Critics argue that a purely functional definition is so broad it loses analytic usefulness. If any unit that provides care, support and shared resources counts as a family, then workplaces, sports teams, religious congregations and even well-run care homes would qualify, stretching "family" until it means little more than "a supportive group." A definition that cannot distinguish a family from other caring associations may be more inclusive but is also less precise, and sociologists who favour structural or relational criteria argue that some account of kinship, commitment or permanence is needed to mark off the family from social bonds in general.

Rejecting the premises

[Rejecting P1] Defining a family solely by the functions it performs cannot distinguish it from any other caregiving group, so the functional criterion may be too broad to pick out families at all. [Rejecting P2] Including foster parents, chosen families and caregivers shows the definition is inclusive, but the same breadth admits colleagues, clubs and institutions, undermining the concept's precision. [Rejecting C] That biological and legal definitions exclude some genuine families argues for widening them, not for abandoning any structural criterion in favour of function alone.