MS is a mystery disease, there is so much that is unknown about it. Right now they say it isn't hereditary, but who knows what the future will bring. They don't 'think' it is, but what about those who do have family members who have MS? Maybe just a strange coincidence, I don't know.
I am the only person that is known to have MS in my family as well. But then again, my mother was adopted at birth, so not a lot is known about her family.
Like I said in my other post, no need to worry about it unless you are having any symptoms of the disease. Best of luck and take care!