To a great extent, I sense that the relationship that emerges throughout the play is one where the son understands better the shortcomings of the father. I think that Biff understands that his father's guidance and beliefs are ones that impact his own chances of being happy. In critiquing himself, Biff understands that he is following his father's footsteps. While his father cannot necessarily find happiness, Biff seeks to prevent himself from going down the same path. The development of their relationship lies in Biff understanding Willy's failures as a father and as a person. This is part of how Biff comes to understand that he should embrace a different path to his life in the assertion that Willy failed by attaching a dollar or material amount to his dreams' success. It is not that Biff becomes closer to his father or seeks to become like him, but their relationship matures in that he understands his father's shortcomings as the play progresses. What might have been seen as his own failure is something that Biff is able to place in the larger context of their own relationship as the play develops.