Category:Individuals by association

 is a meta-category for organising subcategories having to do with individual people's personal associations and loyalties. Thus, you'll find here categories which tag people as:
 * an employee of this business
 * a friend of that person
 * an enemy of this other person
 * a member of a particular organisation
 * a guest on an invitation list at a particular social event

Ultimately, this category could identify people by really any social relationship — even the something so very broad as a category organising the sexual partners of Jack Harkness.