Question: My 13-year-old brother suffers from epilepsy and has to take medication three times a day. How should he observe Sawm (Fast)? Should Kaffaarah (expiation) be paid when Sawm becomes obligatory upon him?
Answer: When your brother reaches puberty by having one of its relevant signs, such as discharging Maniy (sperm), growing of coarse pubic hair, or reaching fifteen years old, it is obligatory upon him to observe Sawm. If he cannot do so because of his illness, it is permissible for him to break Sawm if it is a chronic illness... read more here.