Dean was your big brother along with Sam.

you were the youngest, you were born 2 years after Sam was born, you were raised by them, so you didn't see them as older brothers but almost as fathers, mostly Dean (no wincest!)

Dean had always been protective of you, you were smaller than them, you grew up hunting supernatural things like them after all, he was worried about you.

now you were in the Bunker, you were as good as Sam at research, you were in the war room while you read.

Dean returned from the store and got some beers and something to eat.

Dean:"What are you doing on top of that book you little nerd?" smirk