Is this parkinson's disease?

My grandpa somehow developed this uncontrollable shaking in his right hand back a few years ago and as far as we can tell it's been getting worse. now his arm is all tight and he clenches his hand into a fist while shaking to the point where he can't do a lot of stuff like tie his shoelaces or hold a spoon to eat or write. His left hand as far as I know seems okay (maybe in a semi-fist position, but more mobile than the other hand for sure--and no shaking), but his whole body is kind of stiff. He can't stand up or sit down very easily and is in this permanent slouch position that he can't get out of. He seems to have a bad balance and always wobbles side to side when walking and also shuffles his feet because he can lift them up well. He needs people's help doing a lot of tasks and my grandma has to bathe him and dress him. He also complains a lot about how despite his lack of physical mobility, his mind is crystal clear and he still has great memory and problem solving abilities. After looking at other symptoms of the disease, I was also reminded that it appears like his facial expressions don't change much but when he does laugh, it doesn't seem hard for him to... I don't see my grandpa very often but there does seem to be a very slight worsening of his stiffness each time. We took him to the doctors in the little town he lives in a long time ago and they seem to not be able to tell what is going on. It's not until now that I'm studying psychology that the possibility of a neurological problem popped up in my mind. I searched a bit about his symptoms and I seem to be getting a lot of parkinson's disease results. This makes me very scared... So I'm wondering based off of the symptoms I have described so far, does it seem likely that he has parkinsons?