First off, I love watching it and I think the children are all brill.
But, I can't help thinking that even though they are very mature academically, their emotional maturity seems way behind most other children.
Is this usual?
Does one thing suffer at the hands of the other? 
Another thing that 'fascinates' disturbs me is the way some parents will encourage their children to compete against each other.
Some of the filthy looks these siblings throw at eachother when one is beating the other is just wrong.
You just know that this level of competitiveness is setting them up for having a very cold relationship with their siblings in later life.
It's the parents fault for encouraging it.