Good morning,
You could make a concatenate helper field of all the names and then sumifs off a unique list. This will only work properly if the names are sorted the same (example Joe-Bob-Bill-Jane-Sue have to always be in that order, Sue-Jane-Bill-Bob-Joe, while being the same people would be a different combination. If you can post a spreadsheet I can show you what I'm talking about.
Best of luck,
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