When I was a kid, I decided that I was a cat. My mother did not immediately run out and get me a litter box she told me to get off the floor, and stop being stupid.
Here's my take on kids claiming to be "transgender": In most cases, there is no father in the picture. In the rare cases that there is, the father is extremely passive, and displays the stereotypical "female" traits and the mother has the more "dominant" stereotypical male traits.
I also have to wonder, if this kid decided that he was a parapelgic, would mom put him in a wheelchair and then encourage him to amputate his legs?