
Serena Williams of the U.S. reacts as she takes on her sister Venus during their 2015 U.S. Open women's singles quarterfinals match. Serena won in three sets to move on to the semifinals.

After dropping the first set 2-6, Venus battled back to win the second set 6-1. She lost the third set 6-3.

Venus Williams returns a shot to sister Serena during their quarterfinal match at the 2015 U.S. Open. Venus's serve was broken in the fifth game of the first set, setting her up for a difficult comeback.

Serena and Venus Williams have won 28 grand slam singles titles between them.

Serena and Venus have played each other 27 times in 17 years.

The Williams sisters are the only two women during the Open era to play each other in four consecutive Grand Slam finals.

Venus snaps a photo of Serena and their mother at the Wimbledon Champions Dinner.

Despite being a two years younger than her sister, Serena has won 19 more singles titles than Venus.

Venus lost five Grand Slam finals in a row against her sister in two years.

The last time the Americans met in a major final was in 2009, where Serena was victorious on Wimbledon's Centre Court.