Typically, a person who owns stocks is referred to as a Stock Holder, or even Share Holder. They can also be referred to as an Investor, but that title is not necessarily limited to owning stocks.
Check with the probate court of the state or county within the state where the decedent resided or was domiciled at the state of death. That is where the will will be admitted to probate and once it...
1. When you receive a dividend from the company or 2. When your trading account providing broker sends you a consolidated statement of all your stock holdings...