'Unable to verify email' problem.

I am getting the 'Unable to verify email because it is already in use' error on my daughter's iPod trying to fix her iMessage. I have gone through the steps to figure out where her email is associated, but it's not working. If I use the 'forgot my password' and choose "Email authentication" I don't recieve any emails to her address. If I choose to answer questions, I can't get past the birthday question. We never intentionally set her up with an appleID, but she may have done it without realizing. Is there a way to find out which AppleID her email is associated with?

Separately, on my son's iPod, I went to check his iMessage settings, to help me figure out my daughters. I sign in my appleID (We all share one apple ID and use separate email adresses for iMessage/Facetime... at least that's what used to work) and select his email, and then it just ends up in a loop asking me to sign in and then which email to use. Any clues on that would be great, too.

Thanks!