What Sam Doesn't Know
What Sam doesn't know is the many nights Dean cries in bed. Not sobbing. But tears flowed as an emotional release for all the pain he carries every day.
What Sam doesn't know is how tired Dean is. Emotionally, mentally, and physically from all the hunts, research, the horrible things they saw on a regular basis, and trying to stop the Apocolypse.
What Sam doesn't know is how lonely Dean is now that Bobby is gone and Cas is off the deep end. How much Dean wants that apple pie life. To find a girl he would love forever and have a couple kids with. But he knows it'll never happen. They will never be able to get out of the family business.
Sam doesn't understand how much Dean needs him to stick around. That he can't be without his pain in the ass little brother.
What Sam doesn't know is the depth of Dean's self-loathing. How much he hates himself and holds himself responsible for so much.
What Sam doesn't know is how much Dean misses their mom. Her gently touch, singing Hey Jude at bedtime, her special pies, the warmth of her arms as she hugged him, the gently touch of her hands as she tended to his cuts and bruises.
But what Dean doesn't know is that Sam knows all those things. He knows Dean cries. He heard him a few times after particularly hard cases and Dean thought he was asleep in the motel bed next to his.
Sam knows how tired Dean is. Which is why he tries to let Dean have the first shower, gives him the more comfortable bed, tries to always have pie and alcohol around. And keep Baby clean inside and out.
Sam knows Dean is lonely. He knows Dean wants a family. And it hurts him to know it'll never happen. Sam made a vow to himself, no matter how ugly it got, he wouldn't leave Dean again. Under the tough, rough, and abrasive exterior, Dean was very fragile and sensitive. He would never do well on his own.
Sam knows how much Dean hates himself and it kills him. He wants Dean to see himself how he, Bobby, Cas, and hell, even Crowley, see him. Dean was responsible, funny, loyal, smart, sensitive in his own strange way at times, damn good at making burgers, loving to those in their family circle, and selfless to the core.
Sam knows how much Dean misses their mother. He's heard him cry out her name in the middle of the night. Seen the pain and longing in his face when he'd see a mom with her children.
Sam knows. But, because Dean is Dean, he never says anything so there's none of those chick flick moments Dean hates with a passion. So, he just keeps pretending he never notices and keeps an eye on his big brother.