Involved are 3 Bitcoin holding parties: Alice, Bob and Charlie.

Alice and Bob are considered to be one household, but for accounting purposes, still want separate wallets.

Charlie wants a separate wallet, but also doesn't want either Alice or Bob being able to spend his funds, in order to mitigate against 5-Dollar-wrench-attacks against them. Only after Charlie dies, he wants Alice and Bob to have access. He doesn't trust lawyers.


Secure physical locations:

 * H: Alice and Bob's [H]ouse, all 3 have access
 * V: [V]acation-home, all 3 have access
 * S: \[S\]afe-Deposit-Box, only Charlie has access


2-of-3 Multi-Sig-Setup Alice and Bob

 * H: Trezor1 + Passphrase_Alice + Passphrase_Bob
 * V: LedgerS + Passphrase_Alice + Passphrase_Bob
 * S: TrezorT + Passphrase_Alice + Passphrase_Bob
 


2-of-3 Multi-Sig-Setup Charlie

 * H: Trezor1 + encrypted Passphrase_Charlie
 * V: LedgerS + encrypted Passphrase_Charlie
 * S: TrezorT + plaintext Passphrase_Charlie + decryption passphrase for encrypted Passphrase_Charlie
 * FinalMessage.io GMail's delayed sending to Alice and Bob: Decryption passphrase for Passphrase_Charlie

OR


3-of-4 Multi-Sig-Setup Charlie

 * H: Trezor1 + Passphrase_Charlie
 * S: TrezorT + Passphrase_Charlie
 * V: LedgerS + Passphrase_Charlie
 * FinalMessage.io and GMail's delayed sending to Alice and Bob: Electrum Seed


OR

Since S and Charlie's brain B have a certain connection, they can backups of one another. If Charlie dies, S and B are inaccessible.

So alternativley:

3-of-5 Multi-Sig-Setup Charlie

* H: Trezor1 + Passphrase_Charlie
* S: TrezorT + Passphrase_Charlie + Electrum_Seed_Brain
* V: LedgerS + Passphrase_Charlie
* GMail & FinalMessage: Electrum_Seed_GFM
* Brain: Electrum_Seed_Brain

plus sha256sum of Electrum_Seed_Brain as a passphrase to encrypt content of S (TrezorT+Passphrase_Charlie) and storing this with H and V.

If Charlie dies: H+V+Gmail&FinalMessage

If Charlie forgets Electrum_Seed_Brain: Nothing really happens

If Safe Deposit Box gets nuked: H+V+Brain


What do you think? What's the best way forward? Or something completely different?