Aha. That can be handy at times.
That functionality doesn't exist within Zen Cart at the present time - mostly because Zen Cart intentionally always sends individual emails.
You will have to add input fields to the admin page that collects the info, and then add functionality to supply the proper headers into the destination email so that the additional recipients are processed as desired, as well as supply a means to pass the desired information to the send function.
It might be easier to alter the code to just give you a couple checkboxes for whom to send copies to. Then when you have either or both checked (ie: him vs you), then have the system send another identical email to the checked recipients.
Or just hard-code a request to email both of you with the message anyway -- that way you both have an archive copy of the correspondence.
Kinda depends on the needs.