What is a primary cause of the conflict between Ponyboy and Darry?in the book The Outsiders by S. E. Hinton.

The main cause of this conflict, in my opinion, is the
fact that Darry has been forced to serve as Ponyboy's parent or parents.  Even though
Darry is so young, he has to do this (and he had to give up any hopes of going to
college) because their parents died.

This leads to conflict
for two reasons.  First, it must surely put a lot of stress on Darry.  He has to try to
raise two younger brothers (who aren't that much younger than him) while he works.  He
has to do this at an age when most people do not have much
responsibility.

Second, it makes Ponyboy unhappy because
Darry is his brother acting as his parent.  It is hard for Pony to accept the way Darry
tries to protect him and make rules for him.  Darry is not that much older and yet Pony
has to accept him as the boss of the family.