....and I've been complaining about this since iOS 2. I absolutely can not believe that this basic mail feature has been missing since the beginning and never addressed. There have to be more people out there that send emails to multiple people on a regular basis and don't want to type each individual address.
The "hack" for this is to create a contact and list every address you want to mail to in the email field separated by a comma. I have one named "family" that populates all of my family email addresses. Again, it's ridiculous that I have to do this since I have a "family" group in my Mac contacts.
The iCloud web interface supports group editing and creation in Contacts and group addressing in Mail, but the features do not exist in iOS. I have submitted requests for these features through the iPhone and iPad sections at Apple.com/feedback. (I don't see a way to submit a request for features in the core iOS on this page.) Does anyone know of another avenue for submitting iOS feature requests to Apple?