Happy Birthday to you!
Here is something from the ALS Association (click link for more):
Q. Is ALS hereditary?
A. ALS is directly hereditary in only a small percentage of families. The majority of patients with adult-onset ALS (90%) have no family history of ALS, and present as an isolated case. This is called sporadic ALS (SALS), and although there is likely a genetic predisposition involved, SALS is not directly inherited in a family. Rare exceptions are when familial ALS (FALS) is masked due to an incomplete family history, such as if the patient is adopted or the patient's parents died at a young age. The remaining 10% of persons with ALS have a close second family member with ALS, which is referred to as familial ALS (FALS).
I'm very sorry to hear about your family member. I know somebody whose mother had ALS. It touches the lives of many people, and I'm surprised we don't hear more about it. Hopefully that will change.