I'm glad to hear that your son is seeing a therapist. Hopefuly this can help him to understand himself. Crossdressing is in most cases only a hobby, however for some is an indication of gender identity questions. Be sure that the therapist is qualified to deal with gender idenity. Please make sure that your son knows that youare in his corner whatever road he takes in the future. This is a friendly forum that will offer you a lot of support Please read many of the threads here which will help you understand crossdressing. Good luck and keep us up to date.
Bria