My mother in law is using my e-mail address for her i-pad therefore I created another e-mail address for my wife's i-pad. We encounter a problem when we use facetime as we can call out but we can't receive calls. I want to use my own e-mail address for my wife's i-pad but the system alerts you that it is already in use. How can this be fixed?

You're post doesn't make a lot of sense. Facetime has nothing to do with your email address, Facetime is linked to your phone number. Create an email account for your mother-in-law, then connect her to that account. Then connect your wife's account to your email.
