Honestly I think a lot of why the otherkin community on Tumblr is so damn confusing is because Tumblr strips things of context.
Historically, you’d have a number of central websites and people who were having otherkin experiences would do a search, and find those. And they’d be gathered in one place and you wouldn’t have to constantly redefine terms because everyone new who came in was assimilated into the existing understanding.
And like, I’m not meaning that to sound creepy or paternalistic, or like you can never redefine terms or add terms. But it happened when it was needed, and by community consensus that a new term needed to exist.
Tumblr is the opposite of a community, in many ways; it’s a game of telephone. Things get reblogged and go viral and people are exposed to concepts they’d never have stumbled across otherwise – which is great! But when any one individual post goes viral it doesn’t have an explanatory website surrounding it. The post itself is the only context most people have.
So someone who’s already in the otherkin community says “otherkin is identifying as non-human” – which in itself is simplified from earlier definitions, like “identifying in part or in whole as something other than human”. And then that gets spread to people who reconstruct the meaning of otherkin from that, and from seeing posts about dysphoria or past lives, and eventually you end up with some people saying “I don’t have any past life memories, can I still be otherkin?” or “There are times when I feel human, am I really otherkin?” without realising that yes, all these things and more were covered under the original definition.
Honestly, otherkin in the past was a pretty broad term. It’s hard to link on mobile, but Google for “crisses otherkin faq” and you’ll find evidence that starseeds, multiples, and even furries were counted as otherkin. There wasn’t the hairsplitting that there is today.
If you feel like you relate to the concept of “identifies in some way or aspect as non-human, or believes self to be non-human in some way or aspect”, you can ID as otherkin (if you want to). There aren’t any more complex rules that disqualify you. And while I think “otherhearted” is an important term, please let’s not let it turn into a catch-all for “anyone who does otherkin slightly differently”. Otherheartedness is a separate (if often overlapping) phenomenon. It’s not “otherkin lite” or “alterhuman identity Not Otherwise Specified”, and it’s muddying the waters for both otherhearted and otherkin folks to use it that way.
If you need a catch-all term, alterhuman is it. But don’t count yourself out as otherkin just because you don’t have the typical experience, either. (Again, assuming you want the label. It’s also fine if you don’t, and nobody gets to tell you that you have to have it because you possess certain traits.)