Say you have a brand portfolio like Potpourri Group (click here).
Each brand in the portfolio plays a key role. There are linkages between brands. A couple of brands do they heavy lifting ... they generate new customers via the co-ops, Google, and Facebook. Other brands are linked to the brands that do heavy lifting ... the brand that generates a new customer via a catalog co-op passes the customer along to the brand linked to it. Without the heavy lifting, the brand linked to the acquisition brand dries up.
With a brand portfolio it is critical to understand linkages. If Cuddledown is dependent upon Serengeti for new customers, then Management must make sure that Serengeti has a robust low-cost / no-cost customer acquisition program that generates enough new customers each year to cross over into Cuddledown.
It's not wise to starve downstream brands by cutting customer acquisition in other brands ... you end up starving the whole ecosystem.