Well, since firefox saved your own accounts password you can delete it, and since you have your brothers account password that was sent to you can also delete unless your account was on johnny the you would need to ask one of the admins to delete but if you have an account on stevie then you can delete it yourself. You can also change your current subdomain without deleting your account by going to http://www.heliohost.../scripts/domain then putting in your cpanel username, password and new subdomain (you will need to included the domain where the subdomain will be registered) I am assuming you remember your cpanel password if not then delete your brothers account and do another password reset for your account and that should work.