George Peter Murdock collected data on family units from 85 societies when crafting his sociological theory of the family. He compared this with existing data on a further 165 societies.
By analysing a cross-societal group of family units, Murdock concluded that the shared attributes of all families were a shared residence, economic cooperation, and reproduction. For him, these shared functions defined the family unit.  Any erosion of these attributes, for example if economic mobility forced members of the family to move out of the shared residence, would correspond with an erosion of the family ties. This weakening of the family unit would then have profound negative consequences.
This narrow definition of a family cannot adequately account for families with LGBTQ parents for whom reproduction is not a core function of the family group. Murdock’s definition is also antiquated. The modern family may not share a residence, as economic conditions drive one parent to alternate regions for work. In these cases, economic cooperation may still be common, as one parent often sends remittance payments home to their partner and children, but a shared residence is often not possible.
[P1] In all cultures, families are built around a shared shelter, shared finances, and the act of reproduction. [P2] Therefore, these three criteria make up the sociological definition of the family.
Rejecting the premises
[Rejecting P2] The definition has become antiquated and no longer applies to the modern family.