Well, understanding how they got that way is a completely different matter. You'd have to understand how they grew up, who influenced them, and from what angle they view the world. Cynicism is not hard to achieve in this world.
As for changing them...well, that would be a slow and difficult process, especially if these traits have been around for at least the 8 years you've been observing them. It's very possible they wouldn't be changed, because, as you indicated, they would have to want to change themselves. It would probably involve you having to get close to them and gain their trust in a very full and real sense, and then subtly influencing them to appreciate the things you appreciate, such as selflessness, and getting them to see the distaste in the negative traits they have. That would require a lot of patience, a LOT of patience, because you wouldn't be able to push them -- pushing causes the opposite party to push back, in most cases. You'd have to make them want to be a "better person," which means you'd have to let them respect and admire you, and keep up that image for however long it would take to at least initiate change, which could easily take years.
Or, at least, that's how I see it.