This question will produce many resounding NO!'s in the Otherkin community. However, magical worldviews generally accept anything as possible to a degree, and to answer this question one must first define otherkin well enough to be able to distinguish between yes and no, and you must especially ask whether the truth of being an otherkin lies within one's means of becoming an otherkin. That is, if a person is in every way, shape and form astrally, mentally, etc as inhuman as a reincarnated dragon friend of his, appearing to all psychic senses and tests as a dragon-kin, but was originally born with a quite human soul which is still the same soul now in question, is he an otherkin? Are you an otherkin because you were born outside of the human archetype, or are you currently an otherkin because you are currently outside of the human archetype?
Our souls are far more malleable than anything in the physical world, and it is entirely legitimate to claim artificial otherkinhood by successfully altering your mind, soul, spirit, or whatever it is whose traits define your species. Such an awakening is possible with shaman-types who identify strongly with a totem creature and carry out shapeshifting. The idea would also be familiar to chaos magicians and the like, who temporarily or permenantly adopt whatever parts of whatever magical systems they desire. A means will lead to an end, but an end is rarely defined by its means.
If you know you are not kin but wish, for whatever reason, to become one your best bet is to read up on chaos magic, paticularly paradigm shifting.
-Suigin Flair
(see also {{Awakening}})