Travel insurance policies primarily provide coverage for any new and unexpected illnesses or injuries that occur after the policy comes into effect. Pre-existing conditions and preventive care are generally not covered due to the short-term nature of these plans. Travel medical insurance unfortunatley will not provide coverage for the expected treatment of a pre-existing condition. You can still buy a policy that would provide coverage for your nephew if he should get sick or injured while in the US however it is important to note that nothing you purchase will provide coverage for any treatment for his epilepsy.
Insurance rates are regulated by law. You can't find the same insurance plan for a lower price anywhere else