Steam family sharing can both users be logged in while one is playing a game?
From the steam family sharing FAQ
Can two users share a library and both play at the same time?
No, a shared library may only be accessed by one user at a time.
My question is while two people can't play games at the same time. Can one person play a game while the other who owns the game be logged in?
can both users be logged in while one is playing a game?
Yes, the game's owner being logged in does not prevent other users from playing the owner's shared games.