I've just started with and setting up family 1password, so far it has not been as smooth as I've hoped. I had created a new sub vault for my son and had moved over some of his passwords there. All good, he got access to those passwords after some struggle with initial set up of 1password on his iPhone, turns out the pre-populated email+master key gets clobbered when initial apple keychain is used. Log in to my.1password website work better.
Anyway the real issue I ran into was the from our family account in 1password app on mac OS, I selected Vault->Manage Access to xxx vault and saw that the Main family vault and our sons was accessible. I didn't want our family to be accessible from my son's vault so unticked the family and pressed confirm. It looks like that removed our son's vault from the family account including all those passwords. I believe they are still available and he can see them from his login.
I'm not sure if this make any sense but ultimately I want to undo that vault that got removed from our family master vault, is that possible?
1Password Version: 7.3.2
Extension Version: Not Provided
OS Version: OSX 10.13.6
Sync Type: 1password