Hi arlicohe,
Thanks for your question. This is one I've asked myself, too, as my dad has Parkinson's. In rare occasions, PD sometimes runs in families, but most cases are sporadic. We have a little more information on the subject here: https://parkinsonsdisease.net/basics/. I hope this helps! Thanks for taking the time to comment!
Take care,
Chris, ParkinsonsDisease.net Team Member