Lightning developer guide says that events can be inherited.
A sub component that extends a super component can handle events fired by the super component. The sub component automatically inherits the event handlers from the super component.
The super and sub component can handle the same event in different ways by adding an tag to the sub component. The framework doesn't guarantee the order of event handling.
But it also says that
We don't recommend using inheritance of client-side controllers as this feature may be deprecated in the future to preserve better component encapsulation. We recommend that you put common code in a helper instead.