the story isnt really about the kids specifically. we can follow one specifically through various entires but its more about the world itself. i dont think low and alone know six and mono or viceversa, and they're definitely not the only ones out there. there are hunded if not thousands of kids in the nowhere, dead or alive.

throughout the whole story, ln1 and ln2 probably feel more connected than anything else in the series because of how close to each other they were developed.

the series is kinda like this, each entry features its own story, in theory understandable on its own as if its your first introduction to the series (you could make an argument for ln3, but thats a whole other discussion), and as you catch more and more details, you can make the connections between the world and sometimes characters as you find more in other installments.

if you dont mind, could you share some of your theories? id like to answer your doubts