My father the inventor was "legally" removed from his invention with a contract he signed stating that there was to be a board created. It was a rotating board that had my father start out as president then vice president followed by secretary and lastly treasurer where he was voted out/removed. Trying to reach Harvey Jasper I am no longer seeing everything I saw on the internet regarding the renaming and subsequent sale to Ford Motor Co.
A granted patent is a bundle of rights. Those rights can be owned but after the patent expires (+ 6 months) the rights do not exist, no one can be the owner of non-existent rights.
Also, from the face of the patent, your relative may have never had any personal ownership of the granted patent. He is listed as the inventor but the other three people were listed as assignees at the time of issue. That means that, at the time of issue, they were listed as the owners. There may very well have been later assignments to a company in which your relative was an officer. However, from the face of the granted patented, he did not appear to have any ownership rights at all on the day of the grant.