Marfan's is pretty rough. Used to be lucky to make it to 40 if you had it, but it's fairly manageable now if you know you have it. Just have to be aware of the problems and stay on top of them.
My wife and daughter both have Ehlers-Danloss, which is related connective tissue disorder but nowhere near as bad. They kept an eye on daughter's aortic root, but seems to have "grown out of it" and it's not considered enlarged.
I am STUNNED no one diagnosed him before, he's surely been around a lot of doctors. We were worried our daughter had Marfans, but the doctor took about 30 seconds to say no. Doc said she can walk down the street and diagnose people with Marfans with their clothes still on. It's not something that is hard to see once you know what it is.