Stephen´s family´s opinion and the narrator´s reliability

While reading further and further through chapter 4, we can clearly see how many of the characters in the story underestimate and even mock Stephen and Keith's activity of spying, each character in its own way.

In Stephen's own family, both his mother and his brother Geoff disapprove the fact that Stephen gets together with Keith as often as he does. His mother probably doesn't like this because she sees Keith as some sort of bad influence for Stephen, and this is why she doesn't allow him to go to Keith's house most of the time, as she expresses by saying "Fidget, fidget! What's got into you?" as well as "Now where are you off to? You're not going to Keith's house again tonight, let me tell you that right now". By saying this, the reader is able to realize that what she probably wants is for her son to do other activities rather than getting together with Keith. She even looks for excuses to make him stay: "Anyway, tonight you can just stay in for once. It is Friday after all" and "Also Daddy's home–he never sees you!".

When it comes to Geoff, he doesn't disapprove as strictly and strongly as his mother, but he does it in such a silly way that it's as if he were mocking Stephen and Keith's activities. First, he asks if they're going "after the ape-man on the golf course," and then he hurtfully ridicules Stephen: "I've seen you, chum! Hanging around Mr. Gort's house, looking for ape-men! It's hell's own pathetic, you know, at your age". This demonstrates that he considers their projects to be a waste of time.

Stephen's familys opinion reinforces our belief at this point of the text that Stephen and Keith's activities are no more than a childish game.  We assume Stephen's narration is hyperbolic, as he exaggerates the importance of what they do as if they were going to somehow save tyheir country with their investigation. It just gives us more proof (this time from characters in the story) that their projects might seem great to them but to us (and this time even to Stephen's family) they are just part of an unimportant and insignificant game they've made up in their minds.

As a conclusion, the only thing the whole family's disbelief does is add to the narrator's unreliability. If we already doubted his reliability, both Stephen's mother and Geoff's opinion are going to reinforce our doubts, because they express some of the same disbelief we already had. Like them, we discredit the children's investigation and at this point of the novel we feel really skeptical about their chances of finding anything important.