I always understood it was not inherited/genetic. My father had it and it was always a concern. Now I have experienced some signs of possible early ms, so have been reading everything I can find. It seems that the risk of ms is somewhere around 4 times higher if you have a close relatively with it. It seems to be that there may be some kind of genetic predisposition to react in a particular way to the environmental factors.
What seems clear is that living closer to the equator seems to make you less likely to get ms. Is this because of vitamin d or some other link with more sunlight?