I believe two things were at play in my case (I am not an expert but these is through conversations with my Cardiologis who is also into genetics research specifically around aneurysms and bicuspid valves). First there seems to be a genetic propensity in my family, my brother has 3 brain aneurysms and I know of two other confirmed cases of aneurysm deaths on the same side of he family. My Dr looked for known genetic markers and found none, what led him to believe we may have an an unknown one in my famiy, so they are studying us. Second, in my case and maybe more relevant to others, is that I have a bicuspid aortic valve, according to him there is a relationship between BVs and aneurysms and not only aortic, so in my case that compounded my genetic propensity. Since then I had my children and siblings checked (and my mom) and they are all tricuspid, so only the genetic element is at play with them.