Speaking of parallels...
One (sibling) parallel that is - for the time being - my favourite headcanon, is the Cain/Abel parallel.
I just think of all the looong arches that have been playing out over the past seasons, and I just really really like all the biblical elements.
I like to remember what Cain said to Dean - Abel wasn’t talking to God. He was talking to Lucifer - and I look at Sam, and the little snippets of him we’ve seen in the flashbacks, and I think he has gone waaayyy dark in his quest to find Dean. Like, maybe Lucifer dark. (Remember, this is only my headcanon, not even speculation!)
And seeing as how Dean is Cain’s successor, THAT is a parallel that I really fancy. In my head I see Dean realizing what Sam has done. And that Sam is so far gone that there is no coming back. Dean, however, still feels responsible for Sam, and Sam’s soul, even after everything that’s happened, and after all the shit Dean’s been getting for trying to do what he feels is his job.
So once again, Dean steps up to the plate and does the right thing (shut up, this is MY headcanon), sending Sam to Heaven.
And damning his own soul in the process. Yet again.
Series over.
(As always - if you feel like commenting, please keep me unspoiled...)