I have two DYS with very, very similar scores (1-3 points apart in FSIQ/GAI; different areas of strength, though, and completely different personalities!) and I am very glad that I also decided to have them both tested. I agree with the comment that it is simply much easier to have both in the program. We have attended some gatherings - some a distance away - which would have created all sorts of logistical nightmares if only one was a DYS. Also, DS7 is very quiet at school, so having him become a DYS gives us some resources for him so we can help him develop in his own way (as opposed to DD, who is NOT quiet, so much harder to miss).
For these reasons, yes - do apply.
