can i unlink/disconnect an xbox account from a microsoft account an if so how?

i got an xbox off of my older brother and have always used his account, he now has bought an xbox and we dont want to share an account the account is connected to his microsoft email which is his main email, i have used the account more and would prefer to keep the account with ,y save data and name. is there a way to unlink the xbox account and microsoft account so he can keep his email and make a new account for his new xbox? ive tried waht i thought was changing the email on the xbox account but it turned out i changed the email on the microsoft account.

:)