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:
 * a member of a particular charitable or social organisation
 * a guest on an invitation list at a particular social event

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

Please note, however, that this category generally doesn't house:
 * employees, who are found at category:individuals by employer
 * soldiers, who are at category:soldiers
 * religious leaders and members, who are at category:religious leaders, and Category:Human religion members, amongst other places

Also note that forum consensus has determined that being someone's "enemy" or "ally" or "friend" or "adversary" — or anything similar to that — is far too vague an "association" to be categorised. Thus, the categories of association must be specific and indisputable. The exception to this is the title of "companion", which is vague, but is far too embedded in DW fandom to try to deny. Basically, we accept that Doctor Who fans — and our editors are, after all, fans — will always try to categorise characters by the word "companion", even though there is no in-universe definition of that term, and people therefore always disagree about who "counts" as a companion.