In alternative reality we see Sam fitting comfortably into his life as a cop with a family and we see Dean as a mass killer locked up for life…back story Sam head police chief hunts down Dean 'the demon" Winchester not knowing that Dean is in fact his older brother (he was put up for adoption) *Sam not Dean* Sam finally catches Dean who has gone mad with all the killings.
Fast forward to now. Dean is seen talking to an unknown person –camera pans over- we see it's his secret lover Castiel *I say secret because Dean also is married but his wife bugs the shit out of him and he's happier with Cas but he doesn't want to dishonor his family by getting a divorce*..Cas keeps telling Dean if he doesn't say anything he will, Dean repeatedly tells him to but out of it and that his little brother is happy with his life and he's not going to ruin it for him and that he got out of the lifestyle. Sam walks by and Dean gives him this cold stare…Sam: you look familiar like I've seen you somewhere…Dean: you arrested me Sam: no I know that but that facial reminds me of someone I used to know….Cas: -nervous chuckle- he gets that a lot –side glances Dean- Dean: yea that's it I'm one of those faces you see a lot.
Two weeks later: Dean gets into altercation with another inmate and is crucially injured and his asked is asked by the doctors if he has in living relatives. Dean: no no I don't all my family has died …Cas: Dean stop being stubborn tell them the truth..Dean: Cas I said no we're not bring him into this!...Cas: damnit Dean! Dean: Cas don't I mean it … Doctor: what is it that you're not telling us? – Cas gives Dean a stern look- Dean: fine ill tell them. Chief commander Sam is my little brother he was adopted as a baby because my father I mean our father thought it would save him from a life style of pain. –Sam over hears this- Sam: the hell I don't believe you my parents never told me any of this! Dean: why do you think I look so familiar look in the mirror you were adopted the only reason you don't know about me is because when our father came to see you when you were little he said he was your uncle , that is why my facial expressions trigger a memory if you don't believe me have them check my belongings theres a picture of you and him when you were little. –Sam has an officer bring him is personally belongings- ..-he looks through his stuff and finds picture-.