Hello and thanks for writing. I can understand your concern and would try to help you in the best possible way. Accept my condolences on sudden demise of your brother. The information that you have provided is quite limited to make a clinical diagnosis for the cause of his death. However sudden deaths are commonly due to heart attacks, stroke, cardiac arrhythmia or any other cause. The important thing for you is to be strong in such a tough time. I suggest that you should try not to think about it too much and let the acceptance of his death come slowly to you. You should not let it affect your health.