Tennis-sister superstars Venus and Serena Williams will face off in the Wimbledon final for the fourth time Saturday. The second seed Serena barely edged out Elena Dementieva 6-7 (4), 7-5, 8-6 in today's semifinal, saving a match point with a harrowing backhand volley. "It was really, really tough," Serena told BBC. Venus, meanwhile, easily beat Dinara Safina Thursday. Of the three Williams Wimbledon finals, Serena has won two, in 2002 and 2003, and Venus in 2008. Only once in the last nine years has there been a Wimbledon women's final that didn't feature at least one of the Williams sisters.