Blackouts, strokes and a heart murmur

Patient: My brother is 17 years old. he has had 2 strokes in the last 3 weeks with no common side effects like paralysis or organ failure, nothing has changed since they happened. he also blacks out in high stress situations and has a heart murmur. ive been doing my own research for days and the 3 conditions are hardly correlated. my question is simply if you could point me in the right direction in my research. there is no reason why an otherwise healthy 17 year old should be experiencing these things. if you know of a doctor who could give me some advice please refer me to him.