It hasn’t happened yet, but the Williams sisters got closer today to a rare head-to-head clash, what would be a Family Circle Cup first.

Venus Williams must defeat Madison Keys in today’s quarterfinal and Serena Williams must get past Lucie Safarova to set up a semifinals match Saturday.

The sisters have met 23 times on the WTA Tour with Serena holding a 13-10 edge.

They have not met since 2009 at the Sony Ericsson Championships in Qatar, a Serena victory.

They have played twice on clay: Venus won at the 1999 Italian Open and Serena at the 2002 French Open.

Top seed Serena Williams advanced earlier today with a 6-4, 6-2 victory over American qualifier Mallory Burdette.

No. 5 seed Venus Williams won her third round match against American Vavara Lepchenko, 6-2, 4-6, 6-2.

Follow Gene Sapakoff on Twitter @sapakoff.