Inheritance can be complicated, so consult a professional about that, too. (Or at least give seed words to your inheritors or executors, so they can dominate any arguments.)
This is a good point. When XMR is one day worth $100, $500 or $1000 USD in the years to come. You gonna maybe want to let someone know how to access that juicy XMR wallet(s) just in case you die suddenly (car accident, heart attack etc).
Who to trust the keys to your wallet? I would prefer no one knows until I am actually dead.
Sorry, a bit off-topic I realised.
That is what estate lawyers are for. You can leave the keys to the wallet(s) to someone that do not get to see them until you are actually dead. The legal firm must be trustworthy and, beleive it or not, most are.
One thing you could do is:
1. Use https://xmr.llcoins.net/ to create an encrypted mnemonic seed.
2. Protect your seed as you normally do (safe place, multiple backups, cryptosteel, etc).
3. Give your passphrase to the lawyer (or give instructions on where it can be found), so they can provide this to your beneficiaries when you die.
That way, you control the mnemonic when you are alive, and nobody else has access to the actual seed but you.
edit:
4. Put luigi1111 in your will so that he gets some money when your family asks him how the heck to access the Monero.
Haha
Zip of site on Github (plus signature) is finally updated with the more recent encryption method.