It all depends on what your trying to accomplish. If your wanting to In-Bred Full Bro/Sis together, that usually done for Stock purposes. (Best) You can also Line-Breed Half Bro/Sis together, again usually for Stock Purposes but that only concentrates the common parents genes. (Good) Or, Line-Breed the Parent to its child, usually for Stock. Again this only concentrates that parents genes. (Good) If your going to race any of the offpring to these matings, I would advise Cross-Breeding them to other birds as this is where youll retain your hybrid vigor. Now, there are always exceptions to these rules as I obtained a Stock cock from my mentor who is In-Bred from a Full Bro/Sis mating who turned out to be the '07 YB Champion in my club and also a Multiple Diploma winner in '08 OB's.