"Sub-branding" is a really tricky area. I saw an example of how not to do it in the supermarket today: a new chunky soup (on top) from one of my fave brands, Covent Garden Soup (below).
A sub-brand allows a new product to have a bit more of its own personality, often linked to targeting a new user, occasion or price point. Done well, the sub-brand should tell a "new chapter of the brand story". And the combination of "parent brand" and "sub-brand" should ideally become a single "composite" brand you can remember: Bacardi Breezer, Gillette Sensor, Nescafe Gold Blend etc.
Let's now look at Covent Garden's Big and Bold.
1. Brand new story, not a new chapter
This looks like a new brand altogether. Its a new story, not a new chapter of the same story. This was brought to life by my friend Sarah, a loyal Covent Garden buyer, who was at the same shelf. When I pointed out the Big and Bold packs she said: "Oh, it looks like posh own label that's been put on the wrong shelf." Ow.
Now, let's assume its a good idea for Covent Garden to have a chunkier soup. But this feels like a small change, not a big one. Which would suggest some difference vs. the core range, but not a lot. But Big and Bold has a whole new graphic style and a new pack format (tub not carton).
This is a good example of how range architecture is about the whole visual design, not just the size and position of the brand name. Sure Covent Garden is there on the pack. But you just don't see it.
2. Risks with this approach
The first risk is that people won't know its the new soup from Covent Garden, and so won't try it. The second risk is that any marketing effort for Big and Bold will risk fragmenting the brand's image, as it will have a different tone, style and visual design.
3. Advantages of this approach
The upside of this approach is that the Big and Bold soups stand out on shelf. They also are clearly different from the core soup range. But so many visual brand cues have been thrown away that it no longer feels like Covent Garden.
Net, sub-branding is about balancing brand consistency with ease of navigation. If you work on this, check you get the balance right and tell a new chapter of your brand story, not a new story altogether.