The kid is really really...
...DUMB.
For someone growing up in such a horrible world you would think he would have at least a bit of sense. His father seemed the cautious type, so for him not to pick up on that and follow suit was extremely obnoxious to me. Naivety only goes so far before it becomes cringe worthy and vapid. Case and point, the boy.
He is constantly making noise at the worst moments. Any real kid in his place would likely be silent due to mental trauma, with survival instincts and his fathers influence further instilling a need to STFU!
I have not read the book, but I sure hope this was creative license taken by the screen writer and/or director meant to add tension. However, it made me want the kid to die more often than not, so if that was the case it was very poorly executed.
Perhaps the boy was supposed to be much younger but they wanted an actor of a more amicable age?
Anyways, for me this was another child character that, instead of instilling a visceral reaction, made me intellectually and rationally question his very essence and existence. I cannot fathom how they got as far as they did with his foolishness, especially since it could have only been worse previously. Unless it was a reverse character arch, which is even more annoying.