It's Kind of true to be honest. Like in the opening scene Elwood is ungrateful that he gets picked up in a vehicle that looks like a police car. He also uses coarse language in a disrespectful tone towards Elwood on multiple occasions
I agree that prison time probably made Jake a bit short-tempered, towards his brother. And Elwood, who had been spending Jake's sentence doing little more than waiting for his brother to be released, would also not be interested in Jake's bitching ("Don't yell at me.")
But I always get the sense, when I watch the movie, that Jake and Elwood have got each others' backs, no matter WHAT happens.
I remember laughing a lot the first times I watched the movie when Jake calls Elwood "son of a b*" because they were brothers... (then again, I didn't know they were blood brothers)
As far as I know, blood brothers doesn't mean they were siblings, but became brothers through blood pact (Briefcase full of Blues). Still in many other languages such as Italian being "blood cousins" means that the two people are related through direct family lineage, but I wrote what I ment, the first times I watched the movie I thought they were siblings and it was a cute joke, didn't know they weren't and the orphanage didn't tip me off as many brothers might end up there together.
Yes, I think I understand what you meant, now. They weren't 'blood brothers' in the sense of being BIOLOGICAL brothers who had one parent in common. They were 'blood brothers' because they were raised to be devoted to one another, as brothers.