Is there anyway to figure out what email was used to create a Minecraft bedrock account on PE?

I'm trying to help my brother log into his Minecraft account on his new phone but we can't remember the email we used to set it up. We've tried every email that we could think of but none of them worked. He's still signed into the account on his old phone and I have the DID and MCID numbers if that helps at all.

We've tried to click through to "mange account" and "change gamertag" in the account part of settings but it just sends you to the Xbox login page. I'm almost certain that we didn't make any security questions or link another email/phone number to the account.

:)