Otherkin is a sort of catch-all term for people who feel that, in some way, they are not entirely human.
In a sense, weres are a kind of otherkin, but in general, otherkin refers to people who believe they are
fae, or vampire, or another nonhuman, possibly
mythic type of creature.
There is some crossover between the
therianthrope and otherkin communities, and often while researching one, you'll find the other.
See also