A mother and daughter enrolled in a large introductory sociology class would be considered a:

It is considered to be primary group. It is a gathering held together by insinuating, up close and personal connections, framed by family and ecological affiliations and viewed as fundamental to social life and culture.

A primary group is commonly a little social gathering whose individuals share close, individual, continuing connections. These gatherings are set apart by individuals' anxiety for each other, in shared exercises and culture.