All four of mine get along quite well, and I also think it was due to a lot of deliberate actions on our parts over many years. We pretty much have always required the kids to be nice to each other. We don't tolerate rudeness, name calling, physical fighting, or put-downs. I cringe when I see those t-shirts that say things like "brother for sale." It's not like we talk to our kids about this all the time- it's just been that way for a long time. If we hear an occasional sarcastic comment, we'll pull them aside and ask, "how do you think that made your brother feel?" Or say, "I think your sister was hurt by that comment; I would have been." We don't do the "you must come to every game or piano recital or art show" by your sibing, but we do expect them to be supportive. We also are very much into the "life isn't fair," philosophy, so we make sure they realize that sometimes one child needs attention and sometimes another child needs a new something, and we aren't going to do the same for every kid just because (impossible with four anyways) and I actually think that cuts down on the jealousy.
My kids get along pretty well, too, and we do exactly the same thing. We rarely let them "figure it out on their own," when they were younger, as some books suggest. IMO, they just didn't have the skills to know what was appropriate, and they needed help with that. My kids are also all very different, but I think they're compatible. They go off on their own with their own friends, but do look forward to the time they spend together.
