… neque ei qui pueros ferebant adire ad altam aquam poterant. I had trouble deciding which verb neque went with, ferebant or poterant, because both ways made sense but reading the rest of the story put everything in perspective- neque goes with poterant. I think the clue that I missed is seeing that neque is the first word(excepting the first clause which I omitted) and poterant is the last word and many times the most important words are the first and last with everything else sandwiched in the middle.
That’s right. Another way to think about it is, qui pueros ferebant is a relative clause, and you don’t normally see negators or other important words from the main clause shifted inside the relative clause. Whenever you see a relative clause (or any subordinate clause, for that matter), it helps to mentally put brackets around it:
… neque ei [qui pueros ferebant] adire ad altam aquam poterant.
That way, it becomes obvious that neque is negating the main verb, poterant.
Back in the early chapters when I studied relative pronouns the book suggested the very same thing but over time I tend to forget some of the fundamentals of the grammar.