Lisy, your little nephew is lucky to have an aunt and other family members who can recognize these changes in him and be concerned enough to seek answers.  When a person has CAH, they cannot arbitrarily stop medication.  Replacement hormone therapy is a way of life for anyone with CAH.  Without replacement hydrocortosone, he is in danger of an adrenal crisis which is a life-threatening condition.  Please tell his parents these behavioral changes are a sign that he needs to be seen by a doctor - NOW.  Please keep us posted as to the outcome.