What is the relationship between Willy and Charley?

Charley is a friendly, generous man, and his son Bernard seems sensitive and sincere. Bernard in his youth was what young people call a "nerd" or a "geek." He was obviously not athletic. He was a "drudge" or a "grind," or a "drone," a weakling, "not well liked." He not only becomes a successful lawyer, but he is the kind of lawyer who is permitted to argue cases in front of the U.S. Supreme Court. And he hob-nobs with important people who have their own tennis courts, which means big homes and manicured acreage. It is a case of "He who laughs last, laughs best." There has always been a mixture of friendship and competition between Charley and Willy. That is why Willy won't work for Charley and why he insists he is keeping a strict record of every penny he borrows and insists he will definitely pay Charley back. That may even help to explain why Willy decides to commit suicide. He tells his brother Ben, in one of his hallucinations, he is doing it for Biff.
When the mail comes he'll be ahead of Bernard again!....Oh, Ben. I always knew one way or another we were gonna make it, Biff and I!