Brother

• 1. Introduction

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  Brother: the word itself traces back to Proto-Indo-European roots, to a sound something like bʰréh₂tēr, which flowed into Latin as frater. That single syllable carries thousands of years of human relationship inside it. What does it mean to have a brother? And what has the study of siblings revealed about how brothers shape each other in ways no one fully expected? Those are the questions at the center of this documentary.

• 2. Risk and Warmth

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  Research into sibling relationships has turned up a finding that puzzled scientists. In pairs of brothers, higher warmth between them is linked to greater risk-taking behavior. That pattern does not appear in any other type of sibling pair. Not in sister-sister pairs, not in mixed-gender pairs. Only among brothers. The cause of this connection remains unclear to researchers. What the finding does clarify is something about the limits of warmth as a shield. Sibling conflict is recognized as a risk factor for risk-taking behavior. Yet sibling warmth, at least among brothers, does not appear to function as a counterweight or protective factor against that same behavior.

• 3. Unexpected Biological Effects

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  Girls who grow up with an older brother experience a measurable shift in their development: studies suggest the onset of menarche is delayed by roughly one year. That is a concrete biological effect traceable to the presence of a male sibling. The influence of older brothers extends in other directions as well. Research indicates that the likelihood of a man being gay increases with each additional older brother he has. A separate line of analysis concerns attraction. Some researchers have suggested that a man's resemblance to a woman's brother may increase how attractive she finds him, while divergence from that resemblance may have the opposite effect. Females with a twin brother or a brother very close in age sometimes perceive him as a kind of male alter ego, a picture of who they might have been had they carried a Y chromosome.

• 4. Aristotle on Brotherhood

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  In 350 B.C.E., Aristotle set down his thinking on the bond between brothers in Nicomachean Ethics, Book VIII. His words on the subject were direct: "The friendship of brothers has the characteristics found in that of comrades and in general between people who are like each other, is as much as they belong more to each other and start with a love for each other from their very birth, and in as much as those born to the same parents and brought up together and similarly educated are more akin in character; and the test of time has been applied most fully and convincingly in their case." For Aristotle, this closeness carried a specific obligation for the older brother. The older sibling was meant to model good action, and Aristotle was precise about the mechanism: "by imitating and reenacting the acts of good people, a child becomes habituated to good action." The younger brother does not just observe. He internalizes. Aristotle's account of ethics treated habits as durable once formed. "Once the habits of ethics or immorality become entrenched, they are difficult to break." That permanence is what makes the older brother's conduct consequential. Whatever patterns he demonstrates, the younger brother absorbs them and carries them forward as something close to a fixed feature of character.