[PaulKeeble]

You could do a genetic test, Parkinsons has well associated genetic markers and consumer level companies can do testing of this (and others). 23 and me have a bit on it.

https://www.23andme.com/topics/health-predispositions/parkin...

[mtlmtlmtlmtl]

Although if 23andme say you don't have the genes, you might still have them. Also they'll probably sell your data.

[Palomides]

it's not a trivially heritable disease, genetic testing can't tell you with any real confidence if you'll develop symptoms

edit: you may be able to contact a parkinson's genetics counselor specialist which may be more useful