ABANDONED. Science fiction/fantasy book with multiple plot lines that converge; young boy is attending a school and he has a special position because of his power. There is attack on earth and he is taken to this forum area to wait it out

[Taylor]

I remember bits and pieces of the story:
This book has a lot of footnotes that try and establish this world
There are at least two (but likely more) story lines - a young girl, a young boy are the two I know for sure - they both have some sort of special power
The young girl has an older sister who disappears and she follows her into this hidden forest. She gets taken in and reunites with her sister. The two of them eventually meet up with the boy, and the young girl and boy are trained together by this older man.
At the beginning of the book, the young boy is attending a school and he has a special position because of his power. There is attack on earth and he is taken to this forum area to wait it out (hasn't fully developed control over his powers yet) where he meets three other characters (who I believe also attend the school, but they are older and just normal warrior-type).
There is also this young adult male who lives in a settlement camp and gets thrown into the army - his story converges with the two kids as well. I think there was this weird train station where he sees the little girl use her powers against the government.
There is also this weird time lag when you leave earth. The people who join the army and go into space, if they return, more than a generation has passed.
The end of the book has some alien race attack earth, and a group of individuals leaves earth and closes the gate to earth as they do it so that the aliens are separated - there is a weird network/mesh in space.
I read it last summer I believe so it's not a very old book - probably 2000-2016

[Lobstergirl, au gratin]

Taylor, are you still looking for this or did you find it?

[Kris]

No response, moving to Abandoned folder.

Taylor (OP) was last active on the site in August 2020.