When you attempt to create a new case type, Pega creates a class for it. It is by default placed under <ORG>-<APP>-Work. In other words, this is the parent class. Every class has 2 inheritance settings: pattern inheritance first - which allows to search parent classes for a rule, and directed inheritance - which is basically a jump instruction to another part of the (or a different) class tree.
I don't think you'd need to change the default settings about inheritance.