The term brother comes from the Proto-Indo-European *bʰréh₂tēr, which becomes Latin frater, of the same meaning. Sibling warmth, or sibling affect between male siblings has been correlated to some more negative effects. In pairs of brothers higher sibling warmth is related to more risk taking behaviour although risk taking behaviour is not related to sibling warmth in any other type of sibling pair. The cause of this phenomenon in which sibling warmth is only correlated with risk taking behaviours in brother pairs still is unclear. This finding does, however, suggest that although sibling conflict is a risk factor for risk taking behaviour, sibling warmth does not serve as a protective factor. Some studies suggest that girls having an older brother delays the onset of menarche by roughly one year. Research also suggests that the likelihood of being gay increases with the more older brothers a man has. Some analyzers have suggested that a man's attractiveness to a hetero woman may increase with the more he resembles her brother, while his unattractiveness may increase the more his likeness diverges from her brother. Females with a twin or very close-in-age brother, sometimes view him as their male alter ego, or what they would have been like, if they had a Y chromosomes.
The book Nicomachean Ethics, Book VIII written by Aristotle in ¬350 B.C.E., offers a way in which people should view the relationships between biological brothers. The relationship of brothers is laid out with the following quote: "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 these reasons, it is the job of the older brother to influence the ethics of the younger brother by being a person of good action. Aristotle says "by imitating and reenacting the acts of good people, a child becomes habituated to good action". Over time the younger brother will develop the good actions of the older brother as well and be like him. Aristotle also adds this on the matter of retaining the action of doing good once imitated: "Once the habits of ethics or immorality become entrenched, they are difficult to break." The good habits that are created by the influence of the older brother become habit in the life of the younger brother and turn out to be seemingly permanent. It is the role of the older brother to be a positive influence on the development of the younger brother's upbringing when it comes to the education of ethics and good actions. When positive characteristics are properly displayed to the younger brother by the older brother, these habits and characteristics are imitated and foster an influential understanding of good ethics and positive actions.
- Gracchi, Ancient Roman reformers
- Alec Baldwin, William Baldwin, Stephen Baldwin, Daniel Baldwin, also known as the Baldwin brothers; actors
- John and Lionel Barrymore, actors
- Chang and Eng Bunker, the original Siamese twins
- David Carradine, Keith Carradine, and Robert Carradine, American actors
- Bill Clinton, 42nd President of the United States, and Roger Clinton, Jr., his younger half-brother
- Dizzy and Daffy Dean, Major League Baseball pitchers
- Mark DeBarge, Randy DeBarge, El DeBarge, James DeBarge, and Bobby DeBarge, the male members of the singing group DeBarge
- Emilio Estevez and Charlie Sheen, actors
- Isaac Everly and Phil Everly, The Everly Brothers, singers
- Liam Gallagher and Noel Gallagher, members of Oasis (band)
- Barry Gibb, Robin Gibb, and Maurice Gibb, members of the Brothers Gibb or "Bee Gees" singing group
- John Gotti, Eugene "Gene" Gotti, Peter Gotti and Richard V. Gotti, and Vincent Gotti, New York "made men" with the Gambino crime family
- Jacob Grimm and Wilhelm Grimm, known as the Brothers Grimm, German academics and folk tale collectors
- Matt Hardy and Jeff Hardy, professional wrestlers
- O'Kelly Isley, Jr., Rudolph Isley, and Ronald Isley, Ernie Isley, Marvin Isley, and Vernon Isley, members of The Isley Brothers singer-songwriting group and band, which also included their brother-in-law, Chris Jasper
- Jackie Jackson, Tito Jackson, Jermaine Jackson, Marlon Jackson, Michael Jackson, members of The Jackson 5 and later, The Jacksons
- Jesse and Frank James, Old West outlaws
- John, Robert and Ted Kennedy, politicians
- Eli and Peyton Manning, National Football League quarterbacks
- Mario and Luigi, video game characters
- Billy Leon McCrary (December 7, 1946 – July 14, 1979) and Benny Loyd McCrary, wrestlers known as The McGuire Twins
- Ringling brothers, circus performers and owners
- John D. Rockefeller and William Rockefeller, co-founders of Standard Oil and members of the Rockefeller family
- Thomas "Tommy" Smothers and Richard "Dick" Smothers, performing artists known as the Smothers Brothers
- Dwayne Wayans, Keenan Ivory Wayans, Marlon Wayans, Shawn Wayans, performing artists, directors and producers
- Bob Weinstein and Harvey Weinstein, film producers
- Brian Wilson, Dennis Wilson, and Carl Wilson, members of The Beach Boys
- Marvin Winans, Carvin Winans, Michael Winans, and Ronald Winans, members of The Winans, singers and musicians
- Orville Wright and Wilbur Wright, known as the Wright brothers, pioneer aviators
- Daniel Sedin and Henrik Sedin, professional hockey players
Other works about brothers
- In the Bible:
- Saving Private Ryan (1998)
- Simon & Simon, television series
- Supernatural (U.S. TV series)
- The Brothers Karamazov
- The Wayans Bros., television series
- "Bonanza"(1959-1973) Adam,Hoss,and Little Joe (TV series)
- Mufwene, Salikoko S. For example Beau is brother to Serge as they have the same mother and father."The pragmatics of kinship terms in Kituba." (1988): 441-454.
- Solmeyer, Anna; McHale, Susan; Crouter, Ann (February 2014). "Longitudinal Associations Between Sibling Relationship Qualities and Risky Behavior Across Adolescence". Developmental Psychology. 50: 600–610. doi:10.1037/a0033207. PMC .
- Bereczkei, Tamas, Petra Gyuris, and Glenn E. Weisfeld. "Sexual imprinting in human mate choice." Proceedings of the Royal Society of London, Series B: Biological Sciences 271.1544 (2004): 1129-1134.
- McCallum, Robyn. "Other selves: subjectivity and the doppelganger in Australian adolescent fiction." Writing the Australian child: Texts and contexts in fictions for children (1996): 17-36.
- Aristotle, and W.D Ross. "The Internet Classics Archive | Nicomachean Ethics by Aristotle." The Internet Classics Archive | Nicomachean Ethics by Aristotle. Classics Archive, 2009.
- Rogers Victor, Kelly. "Raising Ethical Kids with Insights from Plato and Aristotle." Smartparenting.com. SMRT, 26 Mar. 2014. Web. 2 Dec. 2014.
- The dictionary definition of brother at Wiktionary