As in previous discussions, I always advocate sharing our seed phrase/private key with our closest loved ones. Otherwise, it would be a waste if something unexpected happened to us, and those bitcoins disappeared with us.
If you lose your bitcoin private keys, you lose your bitcoin. If you passed away and noone inherited your bitcoin private keys, your bitcoins lost too. Loss here is access loss but bitcoin remains on the Bitcoin blockchain, in UTXOs and in Bitcoin total supply.
If you don't have inheritance plan, your bitcoin will be lost as same as around 4 millions of bitcoin were estimated lost forever and it will be considered as unofficial gift and donation to other Bitcoin holders.
Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone.
Lost Bitcoin: 3.7 million Bitcoin are probably gone forever.Your
uninherited lost bitcoins will become inactive and it will be recorded as inactive UTXOs and become more dormant with years like dormant UTXOs with ages of 7 years - 10 years+.
https://www.bitcoinmagazinepro.com/charts/hodl-waves/