You could try collaborative custody, even if a safe deposit box isn't perfect. There are probably no perfect solutions.

keep in mind the greatest loss of funds is due to overcomplication, 'locking yourself out', followed by phishing attacks through text messages and emails usually at random asking for 'private keys' to 'update your wallet' and stupid stuff.

If you do go down the multisig route... don't forget to back up your xpubs.