I used to have a family plan on my 360. Microsoft did away with it and split up the four accounts. My kids can't seem to play the full version of games on their accounts that were bought on my account, but they can play games they bought on their account. Is this yet another "benefit" of the individual plans? Does my son have to buy Minecraft on his account to play it?
Sharing purchased games on Xbox 360?
Yes, unfortunately, you are now going to have to purchase separate games unless certain games allow different player saves, which is extremely uncommon. Now you see why Microsoft did that. They weren't making enough money letting everyone share games so if they split it up into separate accounts, everyone will have to purchase their own copy, thus making Microsoft rich as heck.
Good news is you can usually find used copies of these games online for decent prices and maybe even instant downloads could be an option there. This for ex: http://www.ebay.com/...0840119430
As long as the game was bought on this 360, everybody should be able to play it. It's not nothing to do with the Family Plan, as the problem could have happened anyways.
If you've changed consoles (bought a new one, or got a broken one replaced) then you need to do a license transfer to get the sharing to work properly. http://www.xbox.com/...ox.com/drm has the steps. Even if you haven't try the steps anyways, as the licenses may have gotten corrupted.