If you hold Bitcoin in cold storage or an account like Binance, Coinbase and no one knows your password or encryption code when you pass away, it's gone. It's loss forever. However, here's what you can do. When you pass away your bitcoin can go to your wife  by law if it is owned jointly . Second, you could set up a contract agreement for the key to be passed on to your wife/family through a signed legal document. Something like a beneficiary form. Third way, through a written will.