I am an only child and therefore can not possibly understand this sibling rivarly thing. My oldest two spend most of their lives at each others throats.
My 8 year old relys on his older brother to gain and maintain friends and to fill his social life. There are times when the 12 yearold just takes off to free himself from the tag along.
I can see both sides of their debate. I think it is actually healthy for them to have this time apart. I notice a big difference when they reuinite at the end of the day.
I guess out of the 4 they will all have their turn at one time or the other being the odd man out

Besides they are on two different levels at this time in life. My 8 year old is more into wrestling and talking endlessly about how the girls in his school are irritating
While my 12 year old would rather hang out with his friends talking about how girls are so nice looking. He also spends a lot of time grooming and trying to be cool
My 3 year old he would rather watch Nick Jr and bounce off the wall
Once again the baby she fills her days watching the world around her including the front row seat to our live family soap opera.