Sam and Dean

Sam and Dean have always had a great brotherly relationship. They are both protective of each other and will die for another.

Their relationship has changed throughout the years but they still travel and work together.

Background
Dean is the older to Sam and was always told from a young age to "watch out for Sammy". When the demon killed their mother, it was Dean who carried baby Sam out of the house. Dean is like Sam's protector and Dean views himself like this. So when their father John Winchester went out hunting, Dean would watch over Sam. So Dean would basically cook and protect Sam while their father was out. There was one time though when Dean left Sam alone to play some games. When Dean got back, there was a Shtriga standing over Sam. Dean pulled a gun out, but didn't shoot. Then their father showed up and got rid of the creature. He also yelled at Dean for not watching Sam. This enforced Dean's resolve to protect Sam.

As the boys get older, Sam starts asking questions about what kind of work their dad does and why they always have to move around. Dean lies to Sam and makes a remark. Dean tells Sam their Dad is a Superhero. Sam continues on by asking if its because of mom. Dean gets angry and leaves. He comes back later and gives Sam 'dinner'. Sam reveals to Dean that he found Dad's journal and asks if its true. Dean tells Sam its all true (except for Santa) and how Dad fights these monsters. Dean essentially is the one shows Sam the truth about the world and all its supernatural creatures. Realizing Dad is probably not coming home because of the job, Sam goes to bed upset. Dean feels sorry for his brother and tries to make it up to him by stealing presents from other home. Much to his luck, its all chick presents. Sam thanks Dean anyways and gives him the necklace he was going to give dad. This necklace Dean wears till Season 5.

Sam and Dean also go to high school together for one year (Dean in Gr.12, Sam in Gr.9). Dean displays his protective nature again when Sam gets picked on by a bully in Truman High. Dean threatens to tear the kid's lungs out, but Sam stops him. Dean though wonders why Sam didn't take this guy out (due to their combat training). Sam doesn't want to be the weird kid again, which appears to confuse Dean.

Sometime after that, they continue hunting till Sam wants to go to college. Sam leaves and doesn't talk to Dean for 2 years.

Season 1
"I swore I was done hunting for good. Come on, it wasn't easy, but it wasn't that bad. Yeah? When I told Dad I was scared of the thing in my closet, he gave me a .45. Well, what was he supposed to do? I was nine years old. He was supposed to say, "Don't be afraid of the dark." Don't be afraid of the dark? What, are you kidding me? Of course you should be afraid of the dark! You know what's out there!"

- Sam and Dean

Sam is leaving with his girlfriend when Dean pops in to get Sam to join him in the search for their father. Sam is angry at Dean for even thinking of asking him to go on another hunt. Sam continues on how messed up their childhood was; which Dean appears not to have a problem with. Sam does give in though and joins Dean on the hunt for their father, on the condition they are back for Monday. They head towards dad's last case, only to find he is no longer there. With that fact they continue to work on the case. During which they have their first (on screen) run in with the cops. Sam gets angry when Dean doesn't show the cops any respect, and stomps on Dean's foot to get him to shut up. Dean follows up by hitting Sam's head.