My brother's account isn't letting him use my Gamepass/Gold

It basically gives him the option to rebuy the gamepass even though mines is still vaild

What is the message he receives or what happens when he tries to play that particular game? You explain it is the only game that doesn't work but it doesn't work in what way?

When i go online it shows a Page of thé Xbox gamepass subscription and thé Xbox live Gold even though i got gamepass through home Xbox, i would just play with that account but my younger brother uses it to play on his Xbox and for him it's working to play online it's just for me through home Xbox that it isn't working.

it would be best to have your own separate email and not use your brother's

if you are adding the alias so your brother can use your Xbox account to play your games and/or use your Live Gold/Gamepass then it would be better for him to create his own Xbox account and for you to make the Xbox your Home Xbox, which will allow him to
play your games on his account.

the following link has all the info on setting a Home Xbox

https://beta.support.xbox.com/help/hardware-network/console/my-home-xbox

My Boyfriend is having this issue also,we checked the subscription part of his account and it says he has 3 months gamepass ultimate that he was gifted by a friend and it still isn't letting him play any games online