I don't own anything…
My idea of a werewolf is not the same as the creators of Supernatural, and there are other details that I have changed to fit my story as well.
"Sammy!" Dean called frantically for his brother. "Sam!" he ran out of the vacant house that he had been searching. What could have happened to his brother, this should have been an easy job; it was just a routine haunting. Dean let out his breath in a small huff, it was just like Sam to go and screw it up. Even as he assumed Sam's carelessness Dean knew in his heart that something was very wrong. He approached the Impala at a dead run, but as he was about to open the door he saw a man standing in the shadows. His muscles tensed, preparing for a fight, his instincts told him to shoot first and ask questions later, but he had to find Sam.
"Hello, Dean." The man said.
"Where's Sam?" Dean demanded as he took a step towards the man. The man grinned. "Where is he? And how do you know who I am?"
"He is with my children," the man explained ominously.
"I'll kill you! If you touch my brother, I'll kill you!" the man shifted into a large, gray wolf and vanished into the forest. Dean couldn't believe it, a werewolf. Werewolves had his brother! Dean ran to the Impala and opened the trunk. He grabbed a gun and pocketed a couple handfuls of silver bullets; his eyes then passed over the first aid kit that had remained unused for the last few months than he slammed the trunk and took off after the werewolf.
Sky couldn't believe it, he knew the Winchesters were supposed to be good, but after the easy job of catching Sam he thought it was an exaggeration. Now Dean was tracking him, a seasoned werewolf. He picked up his pace and didn't stop until he reached the house.
"The brother, he's following me!" Sky alerted his family as he came through the door. They had a few moments to prepare before Dean barreled through the door.
Dean took in the scene before him, Sky and his mate stood in the doorway to the kitchen, and their children were crouched in their wolf forms around a figure sprawled on the floor. It only took Dean a moment to realize that the figure was his brother. Sam lay crumpled on the floor, covered in blood. Before they could react, he threw himself at the pups with a feral yell.
Moments later, Dean had forced the werewolves back and was kneeling next to his brother with his gun still pointed at the werewolves. Sam was unconscious and had lost too much blood.