sentences:  Vitali retained the WBC Heavyweight Championship until 15 December 2013, relinquishing his belt in pursuit of his political aspirations in his native Ukraine.The Klitschko brothers jointly run the professional boxing promotion companies ""K2 Promotions"" and ""K2 East Promotions"", as well as the ""Klitschko Brothers Fund"", a charity organization.They appear together on German TV shows and commercials, have a website shared between them, and support each other's training and fights.