Very few professional athletes have dominated their sport as authoritatively as sisters Venus and Serena Williams ruled over women’s tennis during their heyday. Both as individual competitors and as the most successful doubles team of their generation, they amassed a record number of Grand Slam and Olympic titles. Maiken Baird and Michelle Major’s documentary about the duo certainly celebrates their remarkable achievements, but it only hints at the darker aspects of their personal story. The film crew had access to the pair during the 2011 tennis season, which turned out to be a year when the sisters hardly played at all due to various injuries. The majority o...