Can games be shared?

He can only share games on his Home console. In order to share with his sister, he would need to set the Xbox One as his Home. As long as he's signed in on his console, he'll still have access to all of his stuff.

Sure, how about when you purchase account based content a popup warning explaining its tied to an account. They could also empower their customer service agents to rectify situations like mine. I contacted Microsoft customer service as soon as i realized
my mistake.

If you are still confused please head over to this page. It has a nice explanation.

As for that stuff not being shared. That is because it is content bought "In game" Stuff that you spend on a in game store can not be shared because it could easily be used to game the system.

One example of a odd game is the ESO game. The expansions of that game are not shareable.

However if you have an idea on how they can make it more clear feel free to post it here.

Follow that second link I sent and submit that idea.

I am also sure that some of this is on the dev and how they wish in game purchases and content handled.

You cannot share all things with EA Access.

You cannot share Early Access trials and discounts.

You cannot use the EA Access app unless your Xbox account is subscribed.

You can share any EA games from the vault that you have installed with your profile.

You can share any EA games you purchased.

You can share Xbox One Games with Gold that you have installed with your profile.

You can share any purchased games and most DLC.

You can share online multiplayer benefits.

You can share any Game Pass game.