Who's to say it's a fetish? Does he sexualities it? If not maybe it's hit him that in a few short yrs he will be an adult. And these days being an adult suck so bad with the economy and the job market. Maybe he subconscious just wants to erase time and be a child again so he doesn't have to grow up, go to college and/or get a job. Maybe right now he just doesn't feel ready to be an adult and is scared.

I agree u and he need to team up and find a good therapist to help him with this important life transition.