Password managers like bitwarden also have emergency access features which can do this, with the caveat of trusting them to enforce the requirement of access only being granted after a notification to the account holder is not denied in some time period (but unlike the lawyer you're not trusting them with the secret directly)

Apple has this thing called Legacy Contact which allows the same but then built in to the whole Apple account. This includes devices as well as the iCloud ~~and attached keychains. Granted, it is another hoop to jump through compared to presharing keys with each other.~~

It would be nice if your Apple account could be unlocked with some other keys as well apart from the primary one, but I guess that is what Apple calls the “Legacy Contact Key”.

Edit: okay so the keychain is excluded from this. So back to storing each others passwords in eachothers keychain…

I didn't know about bit warden doing this until today! I definitely have to look closer into it, been using 1password for more than a decade and I keep being disappointed. I'd definitely like off-sourcing this to someone instead of building it myself