Grandma, and Uncle Rob, and your cousins, and anyone else you have a long standing relationship with, can use your VaultWarden instance if you let them.

But! You now get to maintain uptime (Rob travels and is frequently awake at 3am your time) and make sure that the backups are working... and remember that their access to their bank accounts is now in your hands, so be responsible. Have a second site and teach your niece how to sysadmin.