Couple faction is the original term in Forever Knight fandom for a group of fans who follow a relationship between two or more characters.
The terms "affiliation" or "faction" were initially applied to followers of particular characters in the show. The earliest couple factions involved the protagonist, Nick Knight, with one of the three likeliest love interests: the Immortal Beloveds favour his romance with the vampire Janette; the Nick and NatPackers favour his romance with the mortal doctor, Natalie Lambert; and the Unnamed Faction favour his relationship with his master, LaCroix, usually interpreted by them as sexual in nature. Another early couple faction, the Valentines, involved Natalie and LaCroix, based on their encounter in the episode "Be My Valentine". On the other hand, a popular challenge couple faction, the UnSuiteds, involved LaCroix with Nick's garlic-loving partner, Schanke, on the principle of the unlikeliest pairing.
Not all couple factions necessarily are interpreted as involving a sexual relationship. In fact, the Cousins of the Knight prefer a non-sexual interpretation of Nick's relationship with LaCroix. In this respect, "couple faction" is not quite synonymous with "pairing" or "ship".
Certain common features may be seen in naming couple factions. The suffic "-Pack" (following the model of the "NatPack" faction) is often seen. "Immortal" appears in the name of some all-vampire factions with a canonical basis; and "Unholy" in trio factions that are seen as challengingly unlikely. The prefix "Un-" is also often seen in the names of unlikely challenge-type factions.
In many cases, the faction name—or an adjectival version—may also be applied descriptively to fan fiction about the relationship, and hence sometimes extended to the relationship itself. Thus an "UnSuited story" will somehow contrive a slash encounter between Schanke/LaCroix; and "the Immortal Beloveds" may refer equally to the characters Nick and Janette (especially in terms of the centuries-long Nick/Janette romantic relationship) as it does to the faction supporting them.