Kin

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Kin, short for otherkin and fictionkin, also called " 'kin" (with an apostrophe replacing the other or fiction part of the words) are people who identify as partially or entirely nonhuman or an entity from fiction. This identity is often involuntary.

The specific identity of someone who's otherkin or fictionkin is often called a kintype (or fictotype if it's specifically fictionkin). Ex: One may have a Sans Undertale Kintype.

Kintypes are not specific to plurality, as singlets can also have kintypes. However, there are some similarities between having kintypes and experiencing plurality, and system members can identify as both plural and 'kin. Some individual system members may have multiple kintypes.

There are also similar related groups, such as therians, otherhearted, or synpaths.

Related Terms
A system that is composed primarily of kintypes can be described as a kin system.

A kinform is a kintype that became a headmate.

'Kins are not the same as fictives or extranths, but both do consider themselves to be nonhuman or fictional to some extent. People in a system can have kintypes and identify as 'kin for being a fictive/extranth, but that does not mean having a kintype is inherently same as being an introject.