Probably a boring answer but I know my grandmother’s credit card information. I live with and help take care of her, so she doesn’t mind sharing it with me. Not like I’m planning to do anything nefarious, but I guess technically it could ruin her financially.
I set up my mom and brother with a multivault password manager (1password) where our vault passwords are saved to a shared vault in case we forget our passwords/die - given the level of familial trust I think it’s an acceptable risk especially with how badly we got burnt by trying to get into utility accounts and the like after my father died.
BitWarden does have something similar via “backup access” and “organisation” vaults. I’ve not looked at setting up either, yet.