So these two must have known one another before the war. I definitely get that impression when they briefly meet again during the tutorial, and you have to choose which you will follow the rest of the way. Were they friends? Were they enemies? Were they friends who fell out because Carlotta was Hadvar's girlfriend, until Ralof did the mattress dance with her?
Then after the war, whichever one of the two you followed spends the rest of his days sitting in the Riverwood inn. While the other vanishes, presumed dead or in hiding.
I am disappointed that nothing more is done with these two characters, who each symbolizes their chosen side. When I think about them, I find it to be very poignant how these two men who knew one another since childhood turned into enemies because of the war. Then afterward nothing happens with them. They do not go on with their lives. They do not reconcile. They do not start a feud like the Hatfields and McCoys. Nothing at all. I think Bethesda could have told a wonderful story about the both of them. It could have illustrated how the war tore friendships apart. A story not about battles and politics, but about people. Something also hinted at between Rikke, Galmar, and Ulfric, who appear to have all fought together in the Great War.
Something like this could have even been used as the meat of a quest. Perhaps one in which the player intercedes between them to restore their friendship? That would seem like a good Nine Divines-oriented quest. Like something Stendarr or Mara might send the character on. Or even just something local townies like Faendal or Sven or Carlotta. Or the character might fuel the fire between them, that leads to a final, murderous confrontation?
In any event, I would at least like to see them both back in Riverwood after the war ends, living in homes of their own rather than the inn. Ralof might work at the mill, and Hadvar at the smithy. Each would make great followers as well, and marriage material. That fact that they are not is one of my big disappointments in the game.
And no, this is not an Imperials vs. Stormcloaks topic. Please leave that to the trillion other threads on the subject.