How do Willy's boys feel about him in Death of a Salesman?

"Death of a Salesman," a classic piece of American literature written by Arthur Miller, tells the story of Willy Loman, a traveling salesman of 34 years who is unable to accept change—within himself, his family, or the society at large. His sons, Biff and Happy, couldn't be more different in their personalities, and it's evident in how they treat their father.
Biff is a deeply flawed 34-year-old, from his inability to hold down a decent job to run-ins with the law. However, he demonstrates a strong desire to mature and grow. He especially looked up to Willy when he was a young star football player; but as he's gotten older, he comes to see his dad's wishes for his life as materialistic and unattainable. Having seen Willy cheat on his mother also tainted the idea of his father as a role model. He now finds his father difficult to communicate with and begins to blame his father for making him arrogant, which he says is the reason his bosses always fire him. He wants his father to simply love him for who he is and feels a need to convey the truth about who he is inside and the problems he feels his father caused.
Happy, on the other hand, is quite different from his older brother, both in terms of his personality and his relationship with his father. He shares his father's deluded sense of over-confidence and dreams of getting rich quick. However, because Willy has always favored Biff, Happy has had to work extra hard to please him. He sticks up for his father and defends him from Biff's tirades. He is desperate for his father's approval and makes that clear in their interactions. Ironically, Happy reveals he's actually become rather despondent about the fact that his life is not working out for him as he planned. Yet he stubbornly clings to the notions his father instilled, and thanks to a misguided devotion to his such principles, continues treating his father as if everything is perfectly fine when it's not.