(I certainly know that Mr. Hurst is not related to Mr. Darcy through the novel. That's why I wrote "Mr. Darcy and his friends had some relations for whom there was some need to blush.")

Darcy could also blush for himself for his behavior earlier, and he did (proverbially - in a way) after Elizabeth refused him the first time. But he was capable of amendment. It seems that aside from Mrs. Bennet, Lydia, and Wickham, the other members of the family were all capable of at least slight amendment. (The ones who weren't are caricatures really.)