Adults, surprisingly. I've noticed that 18+ Otherkin are (half obviously, half surprisingly) adults, not all the fourteen year olds doxxing 'fakes' and threatening suicide because 'theyre not real'
If you want to truly know about what its like to be otherkin, ask an adult otherkin(22+) they know whats up
If they act like an adult IRL and online, then what's the point of identifying as an animal?