At Google I/O back in May, Google announced that they were expanding the sharing functionality that came to family plans on Google Play Music, to the rest of the Play Store. Meaning that you would be able to purchase an app, and everyone in your family plan would be able to use that app too. The same goes for games, obviously. Google didn't announce when it would go live, but according to the updated Google Play Developer Distribution Agreement, it should be going live on July 2nd, which is today. In the updated version of the Google Play Developer Distribution Agreement, there is a new section on Apps and Games sharing in Google Play. It details how a family group would have one manager and different members, and how they can purchase the app or game and then share it with others.
Google also notes that developers have the ability to allow previous purchases to be shared. And not just those that were purchased on or after July 2nd. Google also notes that users will be able to see if previous purchases are eligible to be shared on your Play Store listing page. Additionally, support pages show that family members have to be in Australia, Brazil, Canada, France, Germany, Japan, United Kingdom or the United States. So it won't be available worldwide, but it is available in most of the major countries, at least at launch. This will likely be expanded in the coming months though.
Anyone can create a group of people, and be a family, under Google's standards. You can have up to six people in a family group, which could be all of your friends. And this way you get Google Play Music for around $2.50 each, which isn't a bad price, and is definitely better than paying $9.99 per month. Not to mention you still get YouTube Red. And with the Google Play Family Library, it'll mean that one person can buy a game, and everyone can play it - and no, your data does not get shared across other users accounts.
This new Family Library for apps and games should be going live today. Although many users are not seeing it just yet. So keep in mind that this is likely a staged roll out by Google.