To be totally honest it wasn't until I saw test results that I finally admitted it. DH and I both relocated for work after university and 99% of our friends were found through work (everyone has some sort of BSc+) so we're almost always surrounded by crazy smart people. Coincidentally enough most of them have pretty smart kids so we live in a bit of a bubble. Admittedly, DS7 stands out even among them but we still never really thought that much of it until school was a complete disaster so we got testing to prove them wrong and it was a bit eye opener even for us. In retrospect there were a lot of indicators but really it didn't matter until we entered the school system.
DD5, I still don't know. She is completely different than DS so I guess we'll have to wait and see. We'll likely get her tested eventually but are hopefully holding off for a bit.