This is a great question. While I found some mention of passed Dowager's hump research, there is not much in the way of current research in the specific area of genetic causes. This is not to say it is not being done, however. More often than not the public is not made aware of research until after it is complete. So it is entirely possible that this question is being investigated as we speak!   One thing that we do know is that Kyphosis (the technical term for "hunchback") often runs in families. You can read more about it in this overview. That said, you (or your sons) should see a doctor as soon as you notice any abnormalities. Only a doctor can ensure that it is kyphosis and not something else.