Dean is turned into a vampire before even turning 18, during a hunt that went horribly wrong
according to John, vampires were extinct. He wasn't prepared to encounter one mid-hunt with his sons, whom he'd brought along believing they wouldn't be in real danger
a terrible plan, terrible ideas
Dean ended up being taken over by the vampire. In his desperation to escape, the vampire infected Dean with his blood and fled, taking advantage of John's distraction with his eldest son. Sam was desperately screaming for Dean, but John wouldn't let him near as Dean writhed on the ground. Dean begged for help, for his dad, and as he lay dying, John accepted that he had lost his eldest son, telling Sam to back off while brandishing the largest knife he had; at least he still knew how to kill a vampire.
Sam didn't take it well. It was either John or Dean, so he acted quickly, shooting John in the leg. He ran toward Dean, who was telling him to leave him alone, and dragged his big brother along. With John hurt and bleeding, they had little advantage. They had to get to where the Impala was hidden and flee, flee, flee. Sam threw Dean into the back seat and started the car when John was close, limping and shouting Sam's name
"Sam, Sammy... Dad, Dad's here".
"I shot him in the leg, he'll be okay! Dad's dealt with worse, Dean".
"No, leave me alone, leave me alone, go back, Dad's going to figure it out, Dad's going to be able to..."
"No, Dean! You didn't see it! Dad wants to kill you, he's just going to kill you", Sam could barely see the road. He knew how to drive, but it was difficult without something to give him more height. He also had to reach the pedals, but he managed by pressing the accelerator.
"It's okay", Dean said, "if i have to die, so be it, Sammy... it's okay".
"No, i won't allow it! No, Dean, no, we're going to figure this out, we're going to fix this, okay? I'll fix it, i promise".
At first, it wasn't easy. With Dean newly turned into a vampire and Sam having to look after him, and not even tall enough to pass as an 18 year old, they managed by sheer luck. After a road trip, stealing a few things from the Impala, Sam abandoned his father's car and left in another with Dean so he wouldn't be tracked, and they continued on their way. Dean vehemently refused to drink human blood, so Sam had to make do with animal blood, and although it was unpleasant, Dean agreed to drink it from containers that helped trick his mind; it worked if he didn't see the blood
they spent years running from John, years investigating a cure or a way to reverse it, they also hunted because it suited Dean well, one day Sam realized that Dean was too young, he was too pale, too small, he was far from looking his "real age" (he must have been 26 years old) both physically and mentally, a 17 year boy who looked eternal, while Sam was already in his 22 years and had reached almost two meters, he could barely fit through the doors
an idea for a drawing or writing project when i'm in a better mood, because im so annoyed i couldn't do anything hahaha