Growing up, I shared my Steam account with my brother.
Valve described in its news post how the system works.
The new system replaces Family Sharing.
© Steam
Youll find that not all games support Steams new library sharing feature.
For one, it wont work with any game that requires third-party authentication.
If a developer doesnt want their game enabled for Steam Families, they need to opt-out.
That system restricted users from playing games simultaneously from shared accounts.
You know what, good riddance.
News from the future, delivered to your present.