There is, and when you create a new group as I just did today the new group appears on your iPhone or iPad Mail app listings. This makes it easier to find members of that group to add to mailings, admittedly, but I what I do not see is any way (on the mobiles' Mail apps) to do a one-click selection of that entire group as a Mail target. I believe this was the OP's (and my) intent.
When you look at your list of contacts, there's a button on the upper left labeled "Groups". It seems to give you an option to create groups. I never had the occasion to do anything with it, but surely it's there for a reason like this?
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