Amazon automatically grouping products (variations) for dissimilar SKUs

Amazon seems to be automatically grouping similar SKUs (and sometimes dissimilar SKUs) into variations. For example, we have listings of different varieties of Skittles. Amazon has grouped our 3lb loose listing, with a 1lb funsize packs listing, with a totally dissimilar listing of MNM’s. Not sure why this is happening automatically and looking for a way to prevent this. Any help is greatly appreciated.