Game Pass Ultimate Access for Family Members

You must have Game Pass Ultimate or a series of Xbox One Play Everywhere, you family member must sign in the Microsoft Store with your Microsoft Account to access this games.

Hey SmokeMonster

Thank you for taking the time to post this on the Xbox Forums. We understand that you are experiencing difficulties with other accounts on your console using your Xbox subscription benefits.

As stated by Xbox Forums MVP, Ambassador, and Moderator Smwutches, You need to be signed into your account and configure the Xbox as your Home
Xbox.

Once this is done, any other accounts on your console will be able to use your Xbox subscription benefits. Keep in mind that if you are attempting to install games from the Xbox Game Pass while signed into another account that does not have the subscription,
you may be prompted to purchase this subscription.

However, if you go into the Store itself, and download the game from there, you should not encounter any problems. Once the game is installed, anyone on that console should be able to launch the game.

I hope this was able to clear up any confusion or turmoil this might have caused.

You will have to be on your account to download the games then they should be able to play them from theirs

You'll want to make sure you have the console set as your Home console. https://support.xbox.com/games/game-setup/my-home-xbox

You may have to start the downloads from your account, but they should still be able to play them from their own accounts.

Game Pass itself doesn't share, but the games downloaded from it do.