Alias to my Apple ID email address and my iCloud ID

In my Apple ID account info under “Contactable At” my Apple ID email address is there, however below it is a second email address which is a @icloud.com email address that does not belong to me. It will not allow me to change or delete it.

In my iCloud Mail account under Setting, Preferences, Accounts....the @icloud.com email address that does not belong to me is there again. It will not let me change the @icloud.com email address.

My iCloud Settings shows my Apple ID and iCloud ID match and are the correct email address.

It is disconcerting to say the least that an email address is linked to my iCloud that is not mine. How do I delete it.