Adele Faber and Elaine Mazlish open Siblings Without Rivalry by directly challenging a common, well-intentioned parenting instinct: comparing siblings — even in seemingly positive or motivational ways — which the authors argue tends to intensify rather than reduce sibling rivalry and resentment.

Why comparison backfires, according to their analysis:

• Even ostensibly positive comparisons ("why can't you be more organized like your sister") position siblings as competitors for parental approval rather than encouraging cooperation
• Comparison, regardless of intention, communicates to children that their value is being measured relative to a sibling, rather than recognized on its own individual terms
• This dynamic tends to entrench rather than resolve rivalry, since children who feel chronically compared to a sibling often develop lasting resentment toward that sibling, independent of any specific conflict

This opening reframe establishes the book's core corrective project: identifying well-intentioned but counterproductive parenting patterns around sibling relationships, and offering specific, tested alternative approaches drawn from the authors' extensive parent workshop experience.