How to unrevoke access from my steam family share?

[spongebob gaming]

I family shared with my brother earlier today, and today when he logged back into his account he lost all my games, so i was like oh okay ill just unrevoked then give u access again, the question is how do i do that? I logged back into his account and I cant just set it back up :/

[Ogami]

https://store.steampowered.com/account/managedevices/

Revoke his account there, then set it up again.
If you forgot how, in the client settings under Family activate Family Share and then the user from the list for that PC.