I need clarification on multisig hd wallets. Let’s imagine we have a 2/3 multisig. The first key is generated by the user on a mobile wallet, the second is kept on a server while the third is off-line (for emergencies). In an hd wallet the seed is generated from the seed phrase and, from this, the Master Private Key.
How does the generation of the other 2 Master Keys happen?
What do these keys share?
When new private keys are generated by the user are new keys derived also on the server?