What creates super successful siblings? by Patricia Sellers @FortuneMagazine July 15, 2015, 10:42 AM EDT E-mail Tweet Facebook Linkedin Share icons Leadership talent derives from a mix of nature and nurture. And when you meet siblings who are successful at the highest levels,—like Ari and Rahm Emanuel, whom Fortune Assistant Managing Editor Adam Lashinsky interviewed on stage at Fortune Brainstorm Tech this week—you have to wonder how the DNA and the family upbringing work their magic in combination. Ari, the youngest of three whip-smart Emanuel brothers raised in the Chicago suburbs, is a well-known talent agent and the co-CEO of William Morris Endeavor. Rahm is the mayor of Chicago. When the Emanuel brothers took the stage Monday evening in Aspen, we asked communications expert Noah Zandan to watch and analyze their performance. Zandan is the co-founder and CEO of Quantified Communications, an analytics company that measures and trains C-suite executives to communicate effectively. Using Quantified Communications’ technology platform, which can analyze language and speech patterns and benchmark speakers such as the Emanuel brothers against one another and against best-in-class communicators, Zandan says he learned four things. The Emanuel brothers’ authentic communication style contributes to their success. The language of success is authenticity, according to Quantified Communications’ research. Ari and Rahm Emanuel use significantly more authentic language than the average interviewee. For example, in response to a question regarding competition from William Morris rival CAA, Ari spoke with great candor: Ari: “They’re still stuck in the 90s… I don’t even think about ’em. To be candid.” Adam (moderator): “You don’t… You don’t think about CAA?” Ari: “No. I mean they’re… They’re a third of our size. I compete with them on three things in my life. I kinda think about them.” (Laughter) You don’t always have to be serious to be successful. The Emanuels use abnormal levels of informal, engaging language. You don’t feel like they’re acting or performing on stage. Compared to the average informal interview, the brothers used 4.6x more fun, friendly and informal language. They tell personal stories, and they banter. For instance, when speaking about his accomplishment in improving early childhood education in Chicago, Rahm said: “Thank you for that because that’s the first time Ari has ever applauded for me.” (Crowd laughter). Ari replied: “I did it [clapped] before! I clapped before when everybody else clapped!” Different professions require different communication skills. Ari uses 71% more credibility building language than the average speaker. But in his role as a CEO (yes, even in Hollywood), he has to come across humble about his accomplishments and measured in the way he talks about the future. On the other hand, Rahm, as a political leader, relies on exuding confidence to the public. Rahm speaks with 52% more confidence than his brother. The Emanuel brothers are more fun than the Bush brothers. When the Emanuels were asked whether they had the guts to take on George and Jeb Bush in a cage match, Ari gamely replied: “That’s not risk. That’s pure reward.” It was impossible to find apples-to-apples comparisons of interviews with the Emanuel brothers and the Bush brothers. But in studying various interviews with both sets of renowned brothers, Quantified Communications found that Ari and Rahm use twice as much fun and friendly language than the Bush brothers. Well, you could say that this has more to do with party affiliations than anything nurture or nature could affect.