This one confused me. Can someone straighten out my inferences, please?Let's make younger bro "OP" for convenience's sake.

- OP made a deal with the devil a long time ago to get Brad's life; whatever the price was, it's not clear. Could be OP's soul, could be blood (the Devil has a thing with soul-for-soul kinda prices)

- Devil makes Brad a deal: he will be cured for 30 minutes ["a taste of what’s to come. This one’s on the house.”] in which he has to take a soul. He probably poisoned the mother real bad but she didn't die straight, which is why the Devil kept the clock going ("10 minutes left")

- Brad takes all the time he can to try kill OP. OP manages to "kill" Brad, but the deal is as long as Brad is alive. Yet, the deal was forever (?) Therefore, Brad can't really die until OP does. Their lives are somehow dependent on eachother...and good ol' Brad still wants revenge on OP. In true sadistic Brad nature, he asks OP if he's seen what he did to their own mother to show just how heartless he has become.

The last one really is confusing because of the circular dependence: Brad can't die forever, so OP can have Brad's life forever. Brad can clearly kill OP, then his life ends from OP's stab wound...both brothers get to go to hell for their crimes eternally. I think?

EDIT IN: The true sadistic nature of this tale is that judging by the ending...OP will never be able to confirm my deductions. I wanna say RIP but honestly, both of you are terrible people.