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The man in question is indeed Joe C. from Rapper group:
   http://www.kidrock.com/kidrock.htm
There is a shot of him in a clip there.

Also an article was mentioned in Entertainment Weekly
He is argumentative if he is called a midget or dwarf.

To me, he looked looks a normal kid.

One person stated it was related to steroid use.
There are cases of stunted growth in Children.

But usually they catch up.

http://www.penny.ca