Set Season 1
Sam stared out the window of the hotel room at Dean while he waxed the Impala. "Wax on Wax off" went through his head and he laughed. Every single time Dean waxed his car he made that reference. The muscles in Dean's torso tensed as he carefully rubbed the wax into the glistening black sheet metal, briefly turning it to a dull swirl before he buffed it.
After using his forearm to wipe the sweat from his hairline, Dean absently scratched at a small mark on the back of his left shoulder blade. Sam's mind went back to a time before he went to college, a time when he was still trying to live up to John's expectations and failing. That mark on his brother's shoulder was a permanent reminder of one of the times he failed miserably. All he had to do was load the shotgun. A cartridge had jammed in the cylinder and as a result the spirit had time to throw Dean into a wall that held a metal pot rack, leaving a hole in his brother's shoulder that had healed over to the current scar. For days he'd waited on Dean hand and foot begging forgiveness. Dean had enjoyed having a slave boy for a few days, but forgiveness was never a question for his baby brother. John, on the other hand, had made Sam clean every shotgun, load, reload, empty, clean again for almost a month. For months he told Sam that Dean's scar was a reminder of how careless he was and how he was personally responsible for almost getting his only brother killed.
His eyes traveling farther down his brother's body, Sam saw another scar he recognized. This one, without a doubt, was all his fault. A three inch jagged line that started just above the waist of his jeans on his left side and dipped down below what was visible in Dean's current position. Brothers fight, and they were no exception. But they had one thing that most brothers didn't have. Lots of weapons. It had started innocently enough. Dean ruffling Sam's hair and accusing him of liking a certain girl in his class. At twelve, those were fighting words to Sam and it began. The angrier Sam got the more Dean antagonized until Sam got in a lucky shot and Dean got pissed. Then they were physically shoving and hitting each other. John was on a hunt, so there was no one there to intervene in their quest to do physical harm to each other. Still being the physically little brother as well back then, Sam resorted to anything that would keep Dean from kicking his ass, including swinging or throwing anything in reach. After taking a forced header over the sofa and through a coffee table, Sam saw it under the sofa. Dean's .22 rifle. He didn't aim it at his brother. Murder wasn't his goal. But he swung it up towards Dean to use it to beat his brother off of him just as Dean dove down with the intention of pinning Sam to the ground until he cried. The barrel of the rifle tore a long path in Dean's side as he came down on Sam. Instantly, the older Winchester rolled away, clutching at the bloody wound. When Sam had jumped up to see how bad it was, his concern had been met with a sharp right cross that left him sprawled on the floor. By the time Sam made it to his feet, Dean was already in the bathroom trying to stop the bleeding. It had needed stitches, both boys knew it, but Dean also knew that if they went to the hospital there would be inquiries that would lead to authorities finding out about John being away and the wound being inflicted by his younger brother. So he'd shoved Sam into their bedroom with an order to shut the fuck up and stay away from him. That had convinced 12 year old Sam that his older brother hated him and would never speak to him again. He'd spent the next eight hours until John returned curled in the corner crying.
Blood everywhere, broken coffee table, Dean sprawled on the couch with a bandage on his side, and Sam cowering in the bedroom pretty much told John what he needed to know. He'd dragged the details out of Dean before confronting Sam about the fight. Eyeing the scar now, Sam reached down and touched the back of his thigh, knowing that under his jeans he had his own scar. The one left from the belt John beat him with for using a gun against his brother. John had flown into a rage when he found out Sam had raised a gun to Dean. The beating had gone on for almost fifteen minutes before Dean finally managed to drag John away from the child. Later, after John had gone out to seek a drink to calm down, Dean came back in and meticulously cleaned every cut and welt his father had left on his little brother.
Sam realized Dean was now buffing the wax off the Impala and his eyes roamed across the tan skin to other scars. Many of them Sam could name the place and hunt even if not the date, but there were more now. Maybe more because he wasn't there to watch his brother's back. But no matter what, like the 16 year old Dean who stepped in to stop a brutal beating that even Sam himself now admits he deserved, Dean forgives him. Sam knows the absolute worst scar his brother has is all his fault, his alone, and his to try to ease if not erase. The scar Sam left on his heart when he packed his bags and left his big brother behind for Stanford.