Unlinking Xbox account from a lost email.

This has been an ongoing battle for me for quite some time where I had an email that I originally used to link to my Xbox account way back in season 1 to establish an EA account (that has since been lost). The email was my brothers. I’m still able to sign on to my Xbox and play the account. However, I have since switched to pc and linked my steam to my new CURRENT EA account that I’m making this discussion from and have tried to link my Xbox account in order to cross progress but of course it says it’s linked to the other EA account. The issue me and my brother are having is that he hasn’t been able to recover his Gmail, that we even have the login for, due to a changed phone #, and google refused to be of any help. So is there a way that with proof of ownership, I have purchase history and could be asked any security questions, so that I could unlink the Xbox account from the lost EA account to the new current account that I am using now.