Chances of my children developing MS?

My husband's twin sister was diagnosed with Primary Progressive MS in late 20's. Now in her late 40's she is severely disabled and just had a tube fitted to be PEG fed. She has no quality of life and it's very upsetting to see.

My husband does not have any autoimmune disease but his mother has Sarcoidosis.

We have two children who are 5 and 8 and I am petrified that they could somehow have inherited the gene for MS after seeing how much my sister in law has deterioated.

I know nobody has a crystal ball, but are there any accurate statistics to show what the chances of developing this are based on a paternal aunt connection?

I have read that it doesn't run in families...but threads on this forum say otherwise!