I bought this Kia Soul brand new back in 2011. In late 2015 I purchased a new car (Mustang) and sold the Kia to my elderly father. He drove it for 4 plus years before passing away in 2020. So here are my questions:

The car has basically been sitting in the driveway of my parents house untouched for the past 5 years. About once a year, I'll get it started up and drive around just a bit, get the oil changed, etc. The car currently has 99k miles, about 65k of which are mine from before I sold it to dad. My mother has refused to let me have the car back, even though she no longer drives. Having it in the driveway is a comfort to her. She is finally relenting on this, as I hate to see the car sit there and waste away.

The last time the car was registered was in 2020. We cannot find the title, even though I'd originally given it to my dad when I sold him the car. I will need to figure out how to get it into my name and registered. I'm sure this is a somewhat difficult process.

What other work would the car need? The tires are 3-4 years old but with under 200 miles on them. I am not sure if my dad ever had the timing belt changed…it looks new to my untrained eye but who knows. Any other ideas? Belts and hoses? When I drove it last summer everything worked perfectly. Ideally, I'd like to have it as a second car. The Mustang is nearing 10 years old with 113k and they are not exactly known for reliability.

I think you'll need a death certificate & will or whatever document(probate documents, affidavit of heirship, etc) to get the car in your father's heir's (your mother?) name. Then that person can sell/gift it to you. If you're in Texas there is a FAQ on txdmv.gov for this situation.

Sounds like you've done the right things to keep the car viable even though it mostly sat unused. If you're worried though, just take it to your mechanic and tell them this same history before checking it over.

I might be interested if you decide to sell.