In reply to sj1992:
Your use of the terms 'parent' and 'child' are not correct within UVM. In UVM, a 'parent' class will create a distinct 'child' class. This will create the UVM hierarchy in which you can utilize the uvm_config_db to pass configuration object handles.
When you extend a class, the correct terms are 'base' class and 'extended' class. When you extend a base class, the extended class inherits all of the objects and methods of the base class. Therefor there is no need to utilize the uvm_config_db to pass objects.