You have two very smart children. These tests are snapshots based on their day. Both are gifted.

I can't speak to the scores, but I can remind you that you have to think of the FSIQ to the FSIQ instead of the GAI to the FSIQ.

Both girls are within 10 points of each other, which tends to jive with what I've read about sibling IQ.

Also 4 is very young to be testing, it's supposed to be relatively unstable, you may find that she tests higher on the WISC.