Can you share games on Steam?

Since I'm moving away from console gaming, I will be buying games digitally for my PC, obviously. I have an Xbox 360 and my brother and I have 2 different accounts. 

For example, I buy Arma 2 on my Steam account, but my brother wants to play Arma 2 and he doesn't want to buy it. Can I share Arma 2 with my brother in any way possible without having him play on my Steam account and allow him to play on his own Steam account?

I'm curious because he doesn't want to buy the same game again after I already bought it just to play.

If you don't understand something, just ask and I will explain it better.

Thanks

Sorta http://store.steampowered.com/sharing/

not at the moment, you can always just use the same account, but only one person can be online on one account at any given time

Are you sure? 

https://www.youtube.com/watch?v=ftJh56kwM88

i stand corrected

That is what I need! Thanks a lot for that video. It's exactly what I needed. :D

Yeah, but I don't want him fudging up my DayZ saves or any other game I have.