It does not mean "relating to somebody". It does not mean your favorite, the one you simp for, any of that.
This definition for alterhumanity was made as a result of growing ableism and visibility to the online normal of alterhuman communitites, as well as Tiktok wanting to steal terms and then say "Oh, but we're not crazy like the Tumblr kinnies!", which is a bastard's mindset.
To myself, at least, to kin is to be. Nothing more or less could result of that definition. If I'm kin with (myself), it means I am myself. The splintering of such terms has only led to confusion when just "I am this man on your television," could do just as well.
But if what I know is wrong, what is right, and how is that like?
It is feelings of being something "wrong" or "apart" from the physical vessel you read this with, and I type this with. It is sometimes very painful, but do not frame it as pain or affliction. Again, it is just a state of being. Another state of being.