We can actually deduce here that the book that the author use in the passage is: Sibling relationships.
<h3>Who is an author?</h3>An author is actually known to be a person who writes, publishes and sells the published book. Authors share their knowledge, expertise and experience through writing.
We see in the attached image the passage that completes the question.
Thus, the actual book the author used in this passage is that of sibling relationship.
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