Title of home- ownership ?

Location: Utah

Okay this is a little complicated so if clarification is required please let me know.

My grandfather and his friend bought a house together in 2008. They co-signed and got a loan with PNC bank. A few years later his friend leaves the country and my grandfather takes responsibility and continues to make payments on his own. Jump to 2010 my uncle somehow gets his hands on the deed and decides to sell it to my aunt for like $6000, this has not written agreement it is just a handshake deal.. My aunt then tells my grandfather that because she has the deed she is now their landlord. My grandfather continues to make payments for the house and my aunt now pockets the extra money from renting out the other rooms in the house. 2024 she dies and then her children go into possession of the title and appoint themselves as landlords and they refuse to give it back to my grandfather. They attempted to add themselves to the title but due to the prior mentioned friend also being on the loan/mortgage with my grandfather pnc bank does not allow this. All mortgage documents go to the house under my grandfathers name.

After this long story my main question is. Does possession of the title automatically equal ownership? And if it does not is there a way my grandfather could get the titles replaced? For example calling pnc bank and telling them it was misplaced? I was thinking of calling pnc bank abut wanted to see if that was the right move to make, any advise would be greatly appreciated appreciated