Add products to multiple groups

We have a sample pack which contains two different products. I'd like reviews of the sample pack to show on both the individual product pages, but I don't want reviews on the individual product pages to show on each other's pages.

Currently I have set it up so that all products are part of a group called "Collagen" but this means all reviews from all products (sample pack, cashew and hazelnut) are showing on each others pages.

If I could add products to multiple groups, I can set it up so that the sample pack is part of two groups - one called "Cashew" as well as a group called "Hazelnut". Then I could add the cashew product to the "Cashew" group and the hazelnut product to the "Hazelnut" group. That way, only reviews of the sample pack would show on the individual product pages, and reviews of Cashew would not appear on Hazelnut and vice versa.