Hello and welcome to HCM! Aortic aneurism is caused or exacerbated by various factors including high blood pressure, smoking, atherosclerosis and genetics. Therefore, the damaging of connective tissue (which builds the artery walls) might have an hereditary component. Since you have a family history of aortic anuerisms then it is very likely that your son could be more vulnerable to such condition as well. Also trauma could enhance aortic aneurisms. In this context your son should be extremely carefully when doing sports. I would recommend a thorough evaluation of the risk of aortic aneurism your son might be encountering. I hope my answer helped you!