We've got documentation for that right here!
You can view the accounts your Xfinity ID is linked to by navigating to the Linked Accounts section of Account Details on the Settings page. In order to unlink from an account, you can select the Unlink action next to the desired account. After unlinking, you will no longer have access to Xfinity Services or My Account for that account. To regain access, the primary user for the account will need to add you as a user.
In addition, a primary user can unlink any secondary users from their account by selecting the option to Remove them from the Users view in My Account.
I have two old addresses still linked to my account. I have no active services or bills due for those accounts. Would I be able to get them removed?