What are the motifs in Family by Pa Chin?

Moral purity is a recurring idea. The brothers, especially Cheuh-hui and Cheuh-min, are concerned about moral purity. They fall in love with girls who are pure, beautiful, and full of integrity. One of the reasons Cheuh-hui falls in love with Ming-feng is that she is untainted by the upper-class aristocratic society that he deems to be morally depraved. She is also beautiful and wants to do what is right.