Sibling Rivalry Frequent but not Foregone Listen Download Embed Share Share this on Facebook (Opens in a new window) Share this on Twitter (Opens in a new window) Share this via Email Siblings between the ages of three and seven spend an average of ten minutes of every hour fighting, according to the book, "Nurture Shock" ( Flickr/Aislinn Ritchie (cc:by) ) Produced by New York Times, PRI and WNYC