Removing identical items from grouped layers in legend of ArcMap?

Question

I am using ArcMap 10.5 and in the process of creating a map template for people to use in my team. Part of the template is a map layout with a legend. The problem I am having is that I have some layers which are grouped together (Population points, as seen below) and all have the same symbology. In each map created by users of the template, they may have none, one or more than one of the features in this group activated.

The problem I am having is that if all of them are switched on, they all show up in the legend. I have tried adding only one of the layers to the Legend, but this means that if the end user doesn't add that specific layer to their layout then the legend will not display the key for these groups of items.

I am trying to find a way to label the legend so that if one or more of these grouped layers is switched on, then only one label will appear in the legend (i.e. no duplicates).

Essentially this is what I would like the end product to look like:

Answer 1

I think what you should do here is have another layer that just holds symbology. Call it Pop 7 or whatever. That will be the one that will appear in the legend. Then, take the others out of your legend. You can even turn it off, but you'll need to untick this box on the first page of the legend dialog:

EDIT:

Alternatively, if you do tick that box, put Pop 7 in the population group layer. Then, it will only appear when the group layer is turned on. There doesn't need to be any geometry in the layer, so you don't need to worry about anything appearing on the map face.