Syndicated accounts are not owned by anyone; they automatically collect content from the source feed. You cannot log into a syndicated account, nor can syndicated accounts be deleted or renamed. Other account types cannot be converted into syndicated accounts, and syndicated accounts cannot be converted into other account types.
However, a syndicated account's external feed URL can be changed by in the Syndication (RSS) category, including the username and desired URL. Do not create a new syndicated account with the new feed URL, as this will make the change difficult.