I’m not sure what sort of logic you’re looking for. My logic for my otherkin identity followed the same sort of general pattern as my logic for my gender identy, albeit it took less time to figure out my kintype, because it’s something I’ve known and been certain about for much, much longer.
With my gender, I went through a process of realising that I didn’t fit into category A (that is, in my case, female—the category my birth assignment and society’s perception of me). So I thought I must, therefore, belong to category B (that is, male—I hadn’t heard of nonbinary identities yet, since this was my first foray into any sort of discussion about gender and gender identity). Then, somewhere along the way, I realised that I didn’t fit into category B, either, and I therefore must belong to some as-yet undiscovered (to me, anyway) category. And that’s how I came to discover that I belong to category C—being nonbinary. Specifically, I’m genderfluid. It was a lot of If-Then sort of trial and error.
With my otherkin identity, it followed a similar pattern, but started when I was younger. I knew, I felt in my heart and in my mind, that I was not human. I understood what it meant to be human—that’s what my parents were, and it’s what my brother was, so I should have been human too. But it didn’t fit. I was lucky enough to live in a wooded environment, so I started playing games of pretend. I would play at being different animals, or different mythological species. When I started playing at being Elven, something clicked into place. I found my answer to what I might be if I weren’t human, because up until that point, I hadn’t known that there was any other plausible answer.
This was something I held onto, but shoved to the back of my mind. People had to be human, after all—that’s what my body said I was, and it’s what society said I was. Then I started questioning my gender, and I started thinking…well, if my body and society can’t tell me what my gender is, then why should I believe what they say about my species, too? If it’s possible to find an identity in one category different from what empirical evidence suggested, then why not in another?
Along the way, I found the otherkin community, and I found that there were others who, like me, had found comfort and solace in the idea that they didn’t have to be human, that they could be who they were meant to be, regardless of what their bodies or what society told them they were. To me, that was logical. To me, it followed from one point to another.
If you’re looking more for the “science” to back it up, for the time being, you’ll just have to take our experiences as evidence, because there currently is no scientific research to back up what we know to be true about ourselves. Maybe in the future, science will catch up, and we’ll be able to point to articles and studies that “prove” us right. For the time being, I don’t think we need any outside validation or proof—my existence and the fact that I feel right with my current identity is proof enough for me.
That’s all it comes down to. I feel wrong, like I’m lying to myself and like I’m lost, almost, when I try to claim I’m human, or when I try to convince myself it’s all in my head. I’ve done this with my gender identity as well, and with other truths that I personally know about my world and the way I navigate it. (Note: I mean “truths” in a very personal self-identification sense here.) I know that I feel right when I can be honest with myself, and I feel right in the way I currently identify.
If that’s not a satisfactory answer, then I’m sorry—I wish I could explain better. But that’s all I’ve got for now. Others are, of course, more than welcome to weigh in, as I’m sure our other mods may do as well. Best wishes.