My sister says she has Parkinson's disease. Are family members more likely to get the same thing?

Genetics. Parkinson disease is thought to have some sort of genetic risk factor, although it seems that most cases of parkinson disease are sporadic (meaning they "just happened" and were not inherited). One study showed 1st degree relatives of a person w/ pd to be 2.3 times more likely to get it. A genetic link is more likely when a person gets pd at an age younger than 50.