Trinity University
Cultural Trends, Social Movements & Institutions Affecting Family
While this site doesn't list the functions of the family, it does give background material that helps explain how the family functions exist within society. Looks at the way that society changes families.
Other
Definition of "Family" in Zoning Law and Building Codes
Site offers guidelines to writing a definition of Family for the purposes of zoning laws. Gives constitutionally permissible standards.