Why was Paul so fond of his comrades? Besides being friends to him, what did they each symbolize?

Paul's comrades became his family. He faced life and death situations with them on the battlefield. He ate with them, laughed with them, cried with them and even went to the bathroom with them. They truly were his "brothers in arms". Different friends symbolized different things to Paul. Stanislaus Katczinsky, for example, was a father figure to Paul. You can check out the rest at the GradeSaver link below,

http://www.gradesaver.com/all-quiet-on-the-western-front/study-guide/character-list/