@David Moore & MarkPorterREALTOR - as you noted, you created your usernames with a Google Account - so there's nothing to unlink from. David, in your case just being signed in to your Google Account at the time you created your YouTube username wouldn't have automatically linked you - in fact, if you're signed in to Google when you try to create a YouTube username, we first log you out before starting the YouTube signup process. You then need to sign in again with the Google Account you want to use.
Unfortunately, at the moment we don't have a way to move a YouTube username from one Google Account to another. We'd like to offer that in the future, but we've got to work through some messy details first. Sorry I don't have a better answer for you.