If it's in your own secured wallet it's gone unless you take steps for loved ones to retrieve it. Probably the simplest way is to leave your seed phrase in a bank safety deposit box or other secure place and note it in your will. Then your executor of your estate can access it when you die and it gets distributed to whoever you wish.
There's a book on it too. I haven't read it.
I think you misunderstand the multisig approach. The idea is you have like a 3/5 multisig. Give a key to your lawyer, put a key in a safe deposit box, give a key to a family member and another one to a close family friend, keep one yourself (or whatever, pick the distribution that makes sense). Put the redeem script in your will with a list of where the keys are. The bank or your lawyer aren’t going to collude with your aunt to steal from you, but if you kick the bucket the executor of your estate can legally get at those keys. No one person can unilaterally spend, and you pick key custodians that have legal or social controls that prevent them from colluding to steal.
On the questions you asked at the end of your post:
This book is a good read if you’re thinking a out this issue: Cryptoasset Inheritance Planning: A Simple Guide for Owners https://www.amazon.com/dp/B07BRQ864J/ref=cm_sw_r_cp_api_glt_0PC72G8F0FW2WX1CC2DX?_encoding=UTF8&psc=1
You may want to read Cryptoasset Inheritance Planning by Pamela Morgan: https://www.amazon.com/Cryptoasset-Inheritance-Planning-Simple-Owners-ebook/dp/B07BRQ864J/
The best thing I did was read this book:
https://www.amazon.com/dp/B07BRQ864J/ref=cm_sw_em_r_mt_dp_wD.-Fb6AP83QH
I then combined the advice in the book with some of my own ideas.
I stored my seed words on a Billfodl, which is stored in a fireproof safe, the location of which is known by the executor of my will. https://privacypros.io/products/the-billfodl/
In addition, my Trezor wallet is protected with a passphrase. The instructions I left for the executor of my will provide clues to work out the passphrase, which is based on info that only members of my family would know.
I also provided detailed instructions on what a Trezor looks like, where mine is stored, where to purchase a new one, how to perform the recovery procedure (since my Trezor is also protected with a PIN), etc.
Just in case they're still confused by this bitcoin thing, I also provided the details of a trustworthy third party (accountant) who could help out.
Combining timelock and multisig might be more effective
https://blog.lopp.net/fifteen-men-on-a-dead-man-s-switch/
https://www.amazon.com/Cryptoasset-Inheritance-Planning-Simple-Owners-ebook/dp/B07BRQ864J/
The Pamela Morgan book expands on the Jameson Lopp essay
Take it to heaven, and spend it on bling for my angel wings
USD is the currency in hell. For those with that destination, there's a book
https://www.amazon.com/Cryptoasset-Inheritance-Planning-Simple-Owners-ebook/dp/B07BRQ864J/
HIGHLY recommend this book: Cryptoasset Inheritance Planning: A Simple Guide for Owners https://www.amazon.com/dp/B07BRQ864J/ref=cm_sw_r_cp_api_glt_0H20EYJ9VVZK3EFP0SQC?_encoding=UTF8&psc=1
Well worth the $20.