You can share a Steam library with your family. https://store.steampowered.com/promotion/familysharing

That's what he does, from the comment about accidentally kicking each other out.

No, the new system allows multiple users to play the same game at the same time (unless the publisher explicitely opted out).

Does it? I thought only as many times as there are original licenses in the family. Or is this yet another mechanism?

If you want to play the same exact title, yes. But previous versions would kick you out from playing a shared game if the owner was playing any other title in their library, and they've recently removed that behaviout.

That’s awesome, thank you!