- 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 lover for each other form 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".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.
- Solmeyer, Anna; McHale, Susan; Crouter, Ann (February 2014). "Longitudinal Associations Between Sibling Relationship Qualities and Risky Behavior Across Adolescence". Development Psychology 50: 600–610. .