There are a few times when that happened so I can really understand Andrew Adamson's more expansive memories of the story.

The books are weird that way. I keep thinking stuff happened in them that never actually...happened. Like, Edmund never gets snarky with Miraz in the book, but I'd always assumed he did because he does in both versions of the movie.

However I never had any trouble believing that the children were family.

If you have a sibling, you can recognize their interaction as realistically siblinglike, right down to the way they're sarcastic with each other.

That is one of the reasons I was surprised to see C/E fic that seemed to be movie based. (I say seems because I haven't read it yet.)

Most of my stuff is half movie, half bookverse, but that one is mostly movie based.