Imagine, just for a second, that James and Lily never died and Harry was sorted into Slytherin.
He made friends with Malfoy, and they became such good friends that Harry named him the godfather of his children. He trusted Malfoy more than anyone else, even his parents. Malfoy saw him cry when Harry's parents kicked him out for being a Slytherin, and he gave him a home and a family to go to. It wasn't the best family, but it was better than being on the street. They saw each other through the hard times when Voldemort came back, and the battle of Hogwarts took place.
They weren't deatheater's themselves, but Malfoy's parents obviously were. Lily and James Potter tried to get Harry to fight on their side, but he refused. He couldn't fight his best friends parents. Instead, Draco, Harry, and most of the slytherin house fought alongside their parents.
It was a hard choice, choosing between their family vs. their friends, but in the end, only one student in slytherin died. But that one student was imperative to Harry's and the rest of Slytherin House's entire being. As Draco lay in the dirt, gasping for air, Harry rushed to his side.
"Draco. Draco, please hold on." Harry's eyes were blurry with tears as he cried. Draco assured Harry he would be okay, even if he died. Harry was now hysterically crying as Draco told him it wasn't really goodbye. Just goodbye for now. After a few minutes of Harry hilding Draco up to hug him, he felt his best friend's body go limp.
Harry's cries were the only thing louder than the spells and hexes being fired from both sides. At that moment, though, it seemed as though all the spells stopped making any sound, and the only audible thing was Harry's yells.