It is not typical, but also not completely uncommon. Stroke in a young person is often caused by different diseases than stroke in older people. Unlike the common ailments of old-age, such as cholesterol plaques, irregular heart rhythms, etc., stroke in the young requires a different evaluation.

Things to consider would be 1) Inborn heart ailments - such as a hole in the heart or valve disease; 2) Genetic clotting disorder; 3) Disease of the arteries such as a tear or genetic vessel disease. In addition, if he has very poorly controlled health problems, particularly smoking, diabetes, high blood pressure, or very elevated cholesterol, he may simply have elevated aging of the arteries which caused a more "standard" stroke.

I would have his case evaluated by a stroke specialist. Issues to address are obtaining thorough heart studies - both of the heart structure and rhythm, thorough arterial studies, and thorough clotting studies. At his age, he deserves a specialized evaluation. This may also be helpful in reassuring family members that there is no genetic predisposition to stroke.