US Serena Williams (R) and Venus William

Venus and Serena Williams will go for doubles gold on Sunday. (Luis Acosta -- AFP/Getty Images)

Venus and Serena Williams will go for doubles gold on Sunday. (Luis Acosta — AFP/Getty Images)

US Serena Williams (R) and Venus Williams celebrate after defeating Russia’s Maria Kirilenko and Nadia Petrova in the women’s doubles semifinal match of the London 2012 Olympic Games, at the All England Tennis Club in Wimbledon, southwest London, on August 4, 2012. AFP PHOTO / LUIS ACOSTALUIS ACOSTA/AFP/GettyImages