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"Why Does Only She Get One?" — Sibling Inequity and the Record Gap

By Leon MoriguchiPublished May 15, 2026Updated May 18, 20265 min read日本語版あり
Audience
Parents raising more than one child, particularly families with a school-age older child alongside an infant or toddler

TL;DR

  • ·Around age 7–8 children shift from self-referential evaluation to social comparison, making siblings the natural first target; perceived differential parenting predicts sibling relationship quality more strongly than whether a difference actually exists
  • ·The record gap — firstborns are objectively photographed more — becomes visible in retrospect and cannot be changed, but the response to it can be designed starting now through separate per-child storage and deliberate one-on-one record-keeping
  • ·Building specific evidence ("here's what we kept for you") before the "it's not fair" conversation arrives is more useful than reacting to the accusation after it comes

Contents

  1. Lead
  2. When Social Comparison Begins
  3. Why "Unfairness" Arises: The Structural Reasons
  4. What Record Design Can Mitigate
  5. What You Can Do Starting Tomorrow
  6. Summary
  7. References

Lead

"Why does only my brother get one?" "There are way more photos of her." Moments like these have a developmental explanation. Before deciding how to respond emotionally, it helps to understand what is actually happening — and that shifts how a parent sees the situation.

The grievance usually surfaces as sibling friction, but the structure underneath has several layers: the child's cognitive development, the parent's objectively asymmetric behavior, and the gap in "evidence of love" that has been made visible through the record itself. Looking at each layer separately is the starting point for making sense of it.

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