By "master brand" I mean umbrella brand. The brand that covers multiple product lines that hold individual brands of their own. Take Proctor&Gamble, for example - few recognize the P&G name, but almost everyone knows Charmin, and Pepto Bismol.
Understanding the attributes of your master brand is just as important as understanding those of your customer-facing ones. More often than not, someone else will be distributing Pepto Bismol - but the distributor never directly interacts with the Pepto Bismol brand. Their experience is as a customer of Proctor & Gamble, even if P&G doesn't see it that way.
If your products carry their own brand names, then you also have a master brand. How much time do you invest developing its image as well as the image of the products it represents? What benefit do you think having a strong master brand would have for your business?