It is believed that genetics play a role in multiple sclerosis, even if this is unclear for the moment, and it’s still a matter of debate in the scientific community.

It is known that Eskimos, European gypsies and African Bantu do not develop multiple sclerosis, and that Native Indians of North and South America, Japanese and other Asian groups have a very low incidence.
When it comes to the general population, there is less than a one percent chance of developing multiple sclerosis.

However

The chance of developing Multiple Sclerosis increases in families with where a first degree relative has the disease (mother, father, brother or sister). In the case of identical twins, there is a 30% chance of acquiring multiple sclerosis, while for non-identical twins the chance is only 4%.

Even if these statistics show that genetic factors play an important role in MS, other data suggests that a very important role is played by environmental factors. For example, if the migration occurs before the age of 15, then the chances of developing MS increase or decrease (depending if the area to which the migration occurs has a higher or lower incidence of MS).