Heres my thoughts on spiritual fictional kinning. First: I take ...kinning seriously unfortunately, due to my obsession regarding infinite universes, quantum immortality, and "timeline" divergences that create the universes.

I or anyone, can "have/be the same existence" as a specific fictional character. Given the infinite universes, I could have lived a life exactly as "x" therefore making my existence (then, in that universe) the same as "x".
I don't think authors directly write their stories based off of the current person as they exist right now(regarding the fictional character in question who is being kinned), but the person just happens to have a connection to their (alt universe) existence that just happens to be like the author's work.
With infinite universes, any story that someone comes up with here, will happen to be a reality/timeline in some space. If I were to happen to have memories of my reality then that is the same existence of a character now, and a strong connection, would allow me to say I am that "x". In that situation, I would have lived my life as "x" therefore letting me say "I am/was X".

Why do I continue to say "fictional character" then? You keep saying I and X are real, right?
The answer to that is easy. As I have said above, in our current universe, X would be known as character made up by someone. Someone being X is only about their existence outside of this universe and how it may relate to their current one. In this one, we have memories of being X only in a universe where X is real.
Which is not this universe, because in this one, X should be known as a fictional character, and I will refer to X as so.

Doesn't all this mean anyone could be "x"?
Yes. I, just as any other, have infinite variations and existences due to infinite timelines.
Let me quickly define what it means to "be x in a timeline". It means, that in that existence, we share the same defining experiences, what would be memories, of what we know as "x".
The experience/existence that is shared by "x" is not finite. It is not limited to one timeline. They are infinite. We have infinite existences. I believe, for any given "x", everyone has been that "x" in some time/variation.
It is all a matter of how strong the experience of being "x" expands or relates into our current existence.

What would I define spiritual(fictional for this) kinning as?
You have "memories" that are the same experience of "x's(who is an existence that is not real in this universe)", making it that you have lived the same life as x, though in a different universe. How strong your connection to those memories and the idea of "being x" is a big factor into kinning, as well as how the experience of being x relates/extends into your current existence.

By the way I'm not gonna beat you up or something if you kin for fun.