Hepatitis B is a bloodborne disease, a virus which is not genetic or something that develops. You would have to be an IV drug user or come into contact with someone's blood while you had an open bleeding cut of your own. If your mom and dad did not have it, it was not passed down to you. If you had the vaccine when you were 12 then you are vaccinated for life. Even if you come into contact with it, you would be protected from the vaccine.
I'm a student nurse and I've had the vaccine and work with patients that have hep B every day and I do not worry about it.