To be available the larger unit needs the smaller unit to be available. To achieve this set following dependencies in SETTINGS -> ROOMS -> SETUP ''Dependencies'':
*House - ''Requires Availability in'': Apartment1 and Apartment 2, ''Assign Bookings to'': All Dependency Rooms ''Dependency Level': <ins>Include</ins> Sub Dependencies
*Apartment 2 - ''Requires Availability in'': Apartment2a and Apartment2b ''Assign Bookings to'': All Dependency Rooms ''Dependency Level'': Ignore Sub Dependencies (this is the default)