Game sharing with 3 consoles...

As Smwutches already said, you can only have one console set as your Home Console, which allows offline play.

However, as long as you are signed in on a console with the Gamertag that originally purchased the game, you can still play it with any other Gamertag on that console.

So let's take the following example: You have Gamertags A and B.

Gamertag A purchased "A Way Out", "ACA Neo Geo Metal Slug" and "Aces of the Luftwaffe".

Gamertag B bought the games "Battlefield 1", "Black Ops" und "Battle Garegga".

And you have Xbox console 1, 2 and 3, with console 3 being the offline console.

First you have to be online with console 3, and Gamertags A and B have to set that console 3 as their Home Console and download all the games on it. Now everyone can play these games offline on Console 3.

If you now want to play "Battlefield 1" with Gamertag A on Console 1 or 2, you will have to use a second controller and also sign in Gamertag B on the same console.

While Gamertag A is signed in one console, Gamertag B can also play "A Way Out".

And Gamertag A can play "A Way Out", "ACA Neo Geo Metal Slug" and "Aces of the Luftwaffe" on any console they want, as long as they are able to go online.

The same is true for Gamertag B: They can go to any console in the world, and play "Battlefield" or "Black Ops" or "Battle Garegga".

You can only share on 1 console at a time. On the non-Home consoles, you can still access your content if you are signed in since it is tied into your account. To share across 3 consoles without you having to be signed in, you would need to purchase everything
on at least 1 other account.

Oh, ok! Cause talking with an operator of xbox, he actually said to me that it was possible

thanks anyway!

In order to play offline, you will have to set the console as your Home. Since you can only have 1 console set as your Home at a time, it will remove that setting from the current console it is set to and you will no longer be able to share content on that
console.

You can only have 1 console set ad your Home at a time. So your uncle would not be able to share with both of you at the same time. In the scenario you gave, your cousin would no longer be able to play your uncle's game. It's also recommended that your
Home console be the one you actually use.