Like others, I've had this my whole life (I'm 36) and now my 1 1/2 year old son is getting it, although his twin sister isn't (she has my husband's skin type). This is typically a genetic condition, although it doesn't always show up as severely in some as others.
There is no cure for KP, but there are several different types of treatments that can help regulate it. When I was pregnant, my condition heightened extremely on my thighs which I've read is normal. Rather than list all the various treatments, here is a good site for KP, I've included in the link the page for parents of children with KP:
Until/unless a cure comes about in your son's lifetime, most likely he'll just have to live with it. Honestly, other than a few rude comments in junior high (I had it on my face too), it was never a big deal. I'm sure I was more concerned about it than anyone else!