I own nothing!
He couldn't stand to loose him. Not again. He had lost him once when he left them, left his family to go to some fancy school, trying to live a normal life. He had it too for a while, but it wasn't going to last he had seen what hid in the shadows, and under the bed, the things children swore were waiting to steal them away when the lights were switched off. He could never have the normal apple pie lifestyle he knew that but he could try, try and forget about all the people he could save, all the monsters he could get rid of and all the innocent people he could rid of the demons that plagued them, literally.
But he didn't believe he was built for it, not like his big brother who had spent his entire life looking out for his little brother and following orders from their dad like a good soldier probably saving towns of people while he sat in a classroom and listened to some old balding man go on and on about something he deemed important.
So yeah he lived the life had the girlfriend he swore he loved, he almost had the scholarship to help him go to law school, he was going to become a lawyer and have the cute house with the picket fence and the three kids even have a dog just to add the cherry on top. Then his brother appeared and he knew as soon as he saw him no matter how much he denied it he would go with him because that was what brothers did they looked out for each other and helped them out in their time of need.
That's how Dean saw it when he was making his way to the crossroads just looking out for his brother, he needed him and he hadn't dedicated his whole life to looking after his brother just to have it thrown back in his face now. His own life meant nothing to him, he knew he was going to hell, and he also knew as long as he saved his brother maybe he had a chance to go back and have the life he always wanted, because no matter how much hatred he had for his brother for leaving it was outweighed by the gratitude he had that his little brother was safe, and not purposely hunting down things that wanted to kill him.
That was how he ended up selling his soul, he only had a year left, a year to kill every evil son of a bitch he came across while trying to stop his brother doing anything stupid to stop the deal. If their was one thing he knew it was that no matter the cost he would always save Sammy, and he was ok with that even if it cost his life.