"Options available if a Yahoo Account owner passes away" https://help.yahoo.com/kb/SLN2021.html https://help.yahoo.com/kb/SLN2021.html You could try to imperso

"Options available if a Yahoo Account owner passes away" https://help.yahoo.com/kb/SLN2021.html https://help.yahoo.com/kb/SLN2021.html You could try to impersonate him, e.g. if your grandmother knows the answers to security questions, birth date or the original passwort. But if customer service knows or you tell them the account holder is deceased they'll lock it forever.