In Arthur Miller's Death of a Salesman, how does Ben affect Willy's character?

Ben Loman affects Willy tremendously because his character
is a foil of Willy's.

Older than Willy Loman, Ben was
Willy's support system when their father left the household.  However, the first
difference we encounter in the brothers, aside from their age, is that Ben is
courageous, and set out to look for their father in Alaska.  Contrastingly, Willy is
left defenseless, and alone.

Secondly, Ben was daring and
willing to initiate and take on challenges. One of them left him a very rich man when he
decided to take the risk of entering the African mining business. In contrast, Willy
never became successful and led his life trying to chase after the successes and dreams
of people who led their own goals,namely, Dave Singleman: The man whose success inspired
Willy to be a salesman for the sake of becoming rich
quick.

Third, Ben's success rubs on Willy's ego at all
times. Certainly Willy loves his brother, but it is impossible to maintain a healthy
brotherly relationship when Ben continuously reminded Willy about his lack of
success.

In all, Ben shares the same ambition and desire
for a better life as Willy. However, as often happens in life, success is achieved by
the survival of the fittest. In this case, Ben was the fittest man and became
successful. As a result, Willy had to endure the act of basking on his brother's glory
or accept his own failures.