Accessing Purchased Games on XBox One

You'll want to set the console as your Home console in order to share them with your brother. https://support.xbox.com/games/game-setup/my-home-xbox

Digital content like that goes with the accounts so if you delete the previous owners profile from the xbox then you will lose access to the game and if the previous owner has access to that account and downloads it to a different xbox one and makes the
new xbox one their home console then you would loose access to the game also. which if you currently do not have access to the game without the original profile being signed in then your console is not set as the home console.

so basically since its a digitally purchased game that the license for the game goes with the profile that purchased it then you would need to purchase the game on your profile to have access to it at all times.

If you purchased Xbox One games on the Xbox One, then no, they will not work on the Xbox 360. If you purchased Backward Compatible Xbox 360/0g Xbox Games on the Xbox One, then yes they should work, and following Smwutches instructions should get you access
to them.

That's correct, yes. The game will be accessible on both of their accounts. One thing to note, the account that didn't purchase the game will only be able to access it from the Home Xbox.

Thanks,
Kyle

Which console the purchase was made on doesn't matter. It's which account that made the purchase that matters. A purchase made with the account that uses Xbox B will allow users on Xbox A to access the game since that is the one they made Home. While a purchase made with the account that uses Xbox A would allow access to the game on it's Home console Xbox B. While other accounts can play the games on a Home console, sometimes the account that made the purchase has to be the account that downloads the games to that console.