I want to play Civilization 5 with my younger brother. I own a copy of the game, but my brother does not. On Steam I have shared the game with him, but he can not play the game at the same time as me. Me and my brother are on the same WiFi. I have heard there is a way to do this which has something to do with offline mode?
I'll give you a couple solutions that fulfill the spirit of what Steam allows for sharing a single copy of Civ V.
Simple Hotseat mode: You play on a single computer playing a game of musical chair. Passwords for each player help minimize the chance of information bleed between turns. This technique is a bit faster and has the added bonus of built-in calisthenics.
Giant Multiplayer Robot: Think of it as multi-machine or even multi-time-zone Hotseat. You each download the GMR client. When it's your turn it will download the save, and launch Civ V for you. The client can also be configured to automatically close Civ V when you save at the end of your turn, so that your brother can use it. With in-home-streaming configured, you don't even need Civ installed on the 2nd machine. Family Sharing may also need to be set up between n+1 accounts; Owner (Steam) + n Player (Steam & GMR) accounts. I haven't tested all of the details of this as all my friends have their own copies of Civ V. While slightly slower, this solution allows you to ask for advice here while your brother is taking his turn. ;)
I can't think of any other solution that would not put your Steam Account(s) (and any attached games) at risk...
Another solution would be using the family mode steam provides.
Civilisation V still provides a "LAN" multiplayer.
All you would have to do after having setup the family mode on your brother's computer, would be to launch steam offline on one of your computers, launch Civ 5 and create a LAN game.
I'm not certain this will work since Civilisation could rely on another layer of protection to prevent two people with the same license accessing the same game.
I can not assure you that it is fully compatible with Steam TOS since the family mode should only allow one people to use the shared library at one time (the main owner of the game always getting priority).