So, by now, we've learned what kin is. But what about what kin isn't? Here are two things that are commonly confused for otherkinity.
A 'fictive' is an alter / system member who is or is based off of a fictional character. This is something experienced by those with DID, or 'dissociative identity disorder'. Fictives are often psychologically-based introjects (the process in which a person absorbs aspects of reality into their psyche, resulting in an alter).
Fictives are a result of DID. It is not fictionkin. However, the fictionkin community is oftentimes open to interacting with and including fictives, if the fictive in question is interested in doing so. Whether or not they participate in otherkin communities is a personal choice on each individual fictive's part, but this does not make fictives fictionkin.
Similar things can be said for introjects that are supernatural beings, animals, and so on.
Also called 'delusional attachments', 'ficliterals', and so on. The existence of this is... Controversial.
Delusional misidentification is a delusional phenomena in which people misidentify a familiar person, objects, or self, and believe that they have been replaced or transformed. Recently, it became known that this could include having delusions of being a fictional character. The evidence from psychologists of fictional characters being included in this type of delusion, though, is, well... Spotty. And it became popular via Twitter. So. You can probably get why this is controversial. But I am of the belief that too many people claim to have this to write it off, which is why I am covering it here.
Those who have delusional misidentifications of being characters are not fictionkin, unless they choose to take on that label for themselves. Some people who experience it see it as their delusions interacting with their status as kin. People who are alterhuman / nonhuman / otherkin who feel as if their identity is caused by, rooted in or influenced by a delusion may call themselves endels (carrd jumpscare warning), but others simply stick to referring to themselves with the typical otherkin language. But many (if not most) people who self-identify as having delusional misidentifications do not identify with otherkinity at all.