Valve is ready to bring families (or ten really close friends) a lot closer together, as the company has brought its Family Sharing program out of beta. All Steam users will now be able to share games with others, without compromising their own save progress or achievements.
Family Sharing allows users to grant family members or close friends authorization to download and play their games. They can be shared across ten devices and five accounts. Just remember that two users won't be able to play the same game at the same time and that guests cannot purchase DLC to a title that they do not own.
Check out the handy FAQ on the Steam Family Sharing website for more information about how the feature works.