is willy lomans family responsible for his demise?

I do believe Will's family holds some responsibility for his demise.
Firstly, Linda refused to confront Willy although she knew he was trying to kill himself. If she had at least tried to ask him about it he may have changed his mind. Instead she puts the pipe back in his reach regardless. She also supports his every word, thereby filing him with even more hot air. I believe if she was at least honest to herself and helped him face reality he may not have committed suicide.
Willy's sons were also responsible for his death. Biff caused his father grief by being a disappointment who Willy had placed all his hope in. Then he when he confronted Willy on being a failure himself I believe this pushed Wily to his death even faster.
I also believed that Happy contributed to his fathers demise. This is said because he was an utter failure. He had pride in being the assistant to an assistant. I think his father realized that both his sons were just like him. Failures.