Hmm, interesting well, as you should know the key is to access the assets, and that key cant be shared if you want security. If you've lost the key or anyone doesn't have it he cant access the Bitcoins in the wallet. So you need to pass the key but there is a huge risk haha, as I had mentioned already if anyone has the key he can withdraw all the funds. More interestingly haha in reality people store Bitcoins for their hiers. I use to keep my keys mostly in a place and few of my family members know where. As you know haha Death is the reality and it can be on the head anytime.
Trust is a very costly commodity within the bitcoin system and transferring of bitcoin asset to your heir is not same as you would will other types of assets/properties through a written down document with the benefactor not been able to access those documents until the death of parent's. But with BTC a private key is to be made available to the knowledge of either your lawyer or the benefactor else in sudden death he can't have access to the bitcoin, and that is where the private keys needs to be given to someone who you truly trust because with his knowledge of the private keys he can always have access to the assets wether you're dead or still alive, leaving you with the risk of him hijacking it if he so wish.
Transfer bitcoin to an heir the process can be very complicated it's only an issue if trust that can make it look fairly less risky. That's why we need to have children that are brought up under a moral standard of training so they don't have to abuse responsibility when given, cause for a parent to make open his bitcoin wallet private key to his child or children he is invariably placing a responsibility on them waiting for when he might pass on for them to now completely gain full accessibility to the wealth.