Bobby and Danny?
 

Who are Danny and Bobby from Blood on Blood?

Jon was inspired to write Blood on Blood by the film Stand By Me and how it reminded him of his childhood friends. So, I believe that they are basically fictionalized versions of his real friends.

Bobby and Danny were actually real names. Listen to this performance of Blood On Blood, he tells some of it during the break of the song:

He also made some references during interviews and performances in 1989.