Uncle Bright Star and Windrider always butt heads, which is our big tip off that they're complementary characters. It is through his quarrels with Uncle that we see how steadfast Windrider is in his dream, how passionate he is and how he is willing to step on toes – even the toes of someone he respects and is older than him – in order to achieve his dream. Simultaneously, through Windrider and Uncle's interactions, we see just how stubborn and proud Uncle Bright Star is, such as in not agreeing to let Mother immigrate to America to be with her husband and son. Uncle and Father also inspire one another to do things no one else could, such as Uncle's using a telephone and leaving the Company building after the earthquake.
Black Dog and Moon Shadow are the respective sons of Uncle Bright Star and Windrider, another foil pair. This is our tip off that the second generation will also be at odds with one another, along with the fact that, you know, Black Dog and Moon Shadow are always fighting one another. It's like we say in "Characterization": Moon Shadow works, Black Dog does drugs; Moon Shadow makes money for the Company, Black Dog steals it.