Risk ratios of family members (Taiwan)
 

Epidemiology of PD in Taiwan [1]:

"The risk of developing [PD] was 2.2 times higher for siblings, 1.86 times higher for offspring, 1.59 times higher for parents, and 1.46 times higher for spouses."

"... the clinical variability of [PD] prevalence observed in the Taiwanese population is accounted for by genetic factors (heritability) at 11%, shared environmental factors at 9.1%, and non-shared environmental factors at 79.9%.

Reference:

[1] Alice Melao, Parkinson's News Today, 4th June, 2018
Risk of Parkinson's, Other Disorders Higher for Close Relatives, Study Says