Yes, and I had this long, detailed post typed out, and hit "submit", and it went bye bye... <lol>
Anyhow, I figured the thread could use an insider opinion. In truth, being otherkin's more like being transsexual than it is a form of spirituality. Transsexuals feel that their body is the wrong gender--otherkin feel their body is the wrong species.
There is no set belief system involved--'kin do not know why they are the way they are. Within the 'kin community, you'll find hundreds of discussions on the topic, all people speculating, and trying to figure out what 'kin-ness is, and what causes it. Some folks will hold to one idea with a powerful faith, others will confess to having no idea. Many 'kin have what seem to be past-life memories of being their kin-type. How this could be with such a creature as a faery or dragon, they don't know any better than you do--but they still remember.
Sure, there are a few roleplayers and hangers-on at the fringes of 'kin society, but it's a mistake to think these folk are anything but a minority. In some corners of the web, anyone suspected to be pretending is immediately chased off with torches and pitchforks. <G>
Awareness of 'kin-ness generally develops in early childhood. The vast majority of Otherkin know they're "different" very early on...a good number even know exactly what it is that makes them different, and only discover the otherkin community later on. I personally knew that I was "wolf-souled" as early as age 7 or 8. I didn't discover the therian community until I was in my mid-20s. My story's a very common one in the therianthrope community. It's not a matter of molding what they are to fit the template of the community, but of discovering that "hey, there are other folks out there who are like me...cool".
Psychologists assure us that so long as our odd "beliefs" do not interfere with our overall happiness or ability to get along in society, we are not mentally ill.
Or so several of them have said in public recently. (The television show "Animal Imitators" on TLC included a short segment by the therian community's own Coyote Osborne, who gave a very good showing).
While there are a few folks who go to extremes of behavior, and body modification and the like, most otherkin look just like everyone else.
Vampires are not really otherkin, IMO. By definition, otherkin are people who feel they are other than human in mind/spirit. Vampires just ARE different, perhaps that's why they've been swept under the otherkin umbrella. <G> They're not kiddies who like playing Lestat either, but I'll put off explaning all that lest the conversation become a tad too esoteric and metaphysical.
(Contrary to media opinion, most vampires don't dress the part either, and certainly do not seek attention).
Being otherkin means that you don't see what you expect when you look in the mirror--you don't necessarily understand human folk very well, and you probably don't behave the way other human folk expect, either...at least, not all the time. You learn to "pass", though...most of us learn how to "act normal" before we finish school. It just doesn't come naturally.
If this is some sort of personification of our psyches, it's a powerful one--one that is maintained from our earliest memories to the time we die. People don't stop being Otherkin. Religious beliefs are comparatively transitory. Otherkin may have any sort of faith, and there are athiest 'kin as well, for the record. Some incorporate their otherkin-ness into their religion or spirituality--some don't.
I hope this has shed a bit of light on the subject.