I don't know how it works in other families, but in our home a certain amount of things we buy for our children are bought in pairs. (And if it's something that I like, than we have to buy three of them). The reason for this should be obvious. Kids just don't play well and the jealousy thing will sometimes go on for a long time.
My wife and I have dealt with a chaotic household now for many years. Let's say for about 8 or 9 years. So...ever since they were old enough to walk and talk. Wait a minute. They were fighting before that. So let us say about 9 or 10 years.
Now it never really occurred to me that it was actually happening until one day when Lois and I were at the store buying a present for one daughter and we both turned to each other and said, "We better get two of them." Kind of like their skateboards we bought this Summer.
I remember making a mental note right then and there that that was probably not the best decision a parent could make. But at the time it was the most sound and reasonable one that made sense: Avoid all conflict by any means necessary, thus ensuring a pleasant household environment.
Looking back I think we've actually done a pretty good job between the holidays and birthdays. We've learned to draw our lines so as not to enable one child's expectations, while managing to keep peace in the family at the same time. It doesn't always work out the way we plan, but for the most part it does.
One thing that we're still learning is: Don't double up on musical instruments. It's just asking for trouble.
Four years ago we crossed the border into Mexico. We decided that while we were on vacation in San Diego we would take light rail to Tijuana for some sight-seeing. I think that's when it happened. That's when we started buying in pairs. We'd always done it --clothes and dolls and stuff, but nothing like this. It was a set of lime green and purple ukuleles. Later it would be guitars. This year it's violins. We said NO to the two drum sets; they would have to take turns on the one they had. We also have two keyboards, and though the big one is mine they still ask to use it. They have a dual microphone karaoke sing-a-long set and a play station Sing Star.
What my wife and I neglected to buy was two ear muff sets to put on when the girls get in the mood to start an all girl band or do some karaoke(ing). But we're still learning. And now we have the cell phone thing to deal with. I wonder what's coming next...cars?
Oh hell...it's cars!