My 40 Year Old Son Has Numbness In His Legs

My 40 year old son has numbness in his legs to the point he has an altered gait. Some tingling in arms. He drinks smokes and works on a boat. This started about 6 months ago.
My 36 year old daughter has mildly shaking hands but has recently gotten worse and her head has started to shake.
Maybe not related reasons but curious to me. They live in new Bedford and Maine.