I think that 'in general' oldest kids tend to be more 'adult orriented' and younger sibs tend to be more focused on the older sib. So the older children usually act in ways that are impressive to adult. Plenty of exceptions here, though. Girls also tend to be savy socially enough to 'mask' more effectivly.
Even though one IQ test may give you a true picture of your child's operating IQ, I feel that ethically 'If you have reason to test one, test them all.' It is ok to wait until you have a reason to test, as long as one keeps an open mind about it.
Dottie is correct of course that the vast majority of gifted kids are between 130 and 135 (tail shape) and so lots of them have sibs within 10 points who wouldn't be identified as GT.
Here's a philosophical question: If one child is 'bright' across the board and 'HG' in one subject area, but their IQ falls just shy of the local 'gifted cut off' do they need special educational service? For me, that fact that a child needs special educational gifted service is the ONLY real definition of gifted - so I would say yes! Of course I wouldn't 'knee-jerk' throw them in the gifted program because Grinity says they are gifted - I would find a way for them to learn at their readiness level each subject.
See what I mean?
So once siblings enter the picture, comparisons are going to be made, at least silent ones. This is a perfect time to read a book regarding Gardner's Theory of Multiple Intelligences. The trick is to try and try to keep 'seeing' and keeeping track of who each of our children are as they grow and change, yes?
Smiles,
Grinity
