Is families a common or collective noun?

The word 'families', the plural form of the noun 'family' is a common noun, a word for any family or families.

The word 'family' (or 'families') is a collective noun for groups of people or animals, related or with something in common. Example uses:

The community at Yaddo is a family of artists and writers.

A family of raccoons has been living under the cabin.