My little brothers Microsoft uses my primary email account. How can I change this?

Yes you can change the original email address. This process is called changing the primary alias. The primary alias is the email address that is used to sign in to the account. The article explains how to complete this process.

Hi there,

you can't merge accounts itself or fully move the Xbox Live Account to a different Microsoft Account, but something that could work for you is changing the primary email address for the Microsoft Account.

My assumption what steps might be required are:

- Change the primary email on the New Unused Xbox Account account to something else (you might need a new MS account/email for that) so that the Wanted email address is no longer attached to a Microsoft Account.

- Change the primary email on the Old Xbox account to the new wanted email address, so that that Wanted email address can be used to sign in to the Xbox main account.

See this link for the full information on how to change the primary email address on a Microsoft Account

https://support.xbox.com/my-account/microsoft-account/change-email-sign-in-for-microsoft-account

Let us know the results

the hacked manage to delete the email i use for that microsoft account and changed his/her email as primary email,
and also hacker manage to remove my phone number from the account also.

so how can i prove its my account when hacker manage to delete my email use for the microsoft account and change all the my profile info??

Any digital purchase is bound to the account that purchased it however you can change the primary email of an account.

How to change the email address associated with your Microsoft account

https://support.xbox.com/en-US/my-account/microsoft-account/change-email-sign-in-for-microsoft-account

You can change the primary email alias on the account