Old Email

Hey there John! Just to clarify, you have a Child Account, but it's currently attached to the wrong Parent, is that correct? In that case you'd need to first log in to the old Parent Account and remove the child from the Family Menu on the Settings Hub.
The next time the Child Account logs in, it should prompt for a new Parent Account. Just enter the Parent Account info on those prompts and you're all set to go. Let us know if you have any questions on that, thanks!

You can chance the email you get correspondence to, but not the one you sign in with. I still have my college girlfriends aol login from 2006

Hi there Mike welcome to the community forum! Christopher here, an Xbox fan just like you and has been on Xbox for years already. I would really love to make your day by helping you out. You can try contacting the recovery team!

Choosing the “forgot password” option will send you a link to fill out some questions and information so Microsoft can verify that is your account, then you need to wait for Microsoft to contact you for more assistance and the recover your account!

That is so simple!

Sign in your account to
https://account.microsoft.com/profile/ and click on Manage how you sign in, enter your email as the secondary email and set it to Primary, you will be asked to verify the account by sending you a code to the Grans' email, enter the code to get your email
as the Primary. Your Grans' email will be transferred to secondary and you can delete it as long as it isn't a Microsoft email (outlook or Hotmail) or else her email will be deactivated forever. Once done, you can sign in your account using your own email.

I think it is not possible but to be sure contact support