sentences:  Klitschko brothers
  
  Vitali Klitschko (born 19 July 1971) and Wladimir Klitschko (born 25 March 1976), known as the Klitschko Brothers, are Ukrainian former professional boxers.During their peak years between 2004 and 2015, they were considered the dominant world heavyweight champions of their era, and among the most successful champions in boxing history.