CHARLESTON, S.C. -- Top-ranked Serena Williams ended a long and successful day for the Williams family as she and sister Venus both won twice Friday to reach the Family Circle Cup semifinals and set up their first sibling showdown since 2009.

Serena won her 13th straight match by defeating sixth-seeded Lucie Safarova, 6-4, 6-1. Earlier, she topped two-time NCAA doubles champ Mallory Burdette in a third-round match moved due to Thursday's 7 1/2-hour rain delay.

Venus also had double duty, rallying past Varvara Lepchenko in three sets before ousting 18-year-old Madison Keys later on Billie Jean King Court.

The Williams sisters next go for a spot in the finals Saturday. They haven't met in a tournament since the 2009 Tour Championships in Qatar. Serena holds a 13-10 lead, although they're 1-1 on clay.

"For the record, we've never played two matches on the same day," Serena told the stadium crowd. "You guys had a real treat."

They surely did. The sisters were the first four matches on the stadium court - and they only dropped one set combined.

"I was thinking it was a quadruple-header," Venus said with a laugh. "I don't know if that's ever going to happen again."

The excitement continues Saturday when the sisters go against each for a 24th time in their stellar careers at a venue where both have enjoyed championship moments.

Serena is seeking her third Family Circle title after wins in her last two appearances here in 2008 and 2012. Venus took this title in 2004 and scored the clinching points last September when the Washington Kastles took the World Team Tennis crown at Family Circle Tennis Center.

Serena, 31, comes in as world No. 1 having won Wimbledon, the Olympics and the U.S. Open since capturing last year's Family Circle. She added to her haul with a sixth Sony Open crown, rallying past Maria Sharapova for her 48th career WTA crown.

Venus has struggled with illness and injury in recent years. She took some six months off after being diagnosed with Sjrogen's Syndrome, an autoimmune disease, and withdrew from the Sony last month because of a sore back.

Still, Serena is wary of her sister's game and desire to win.

"When I play Venus, it's never an easy opponent," she said. "She's my toughest opponent I've ever played, and I think she's beaten me the most of any player."

Venus, who'll turn 33 in June, has lost four straight to Serena since a victory in Dubai in 2009. The older Williams hasn't won a major since Wimbledon in 2008.

"The last years have been challenging and at some points difficult," Venus said. "But I think in both of our heads, we never gave up on tennis or ourselves."

There's another side of the bracket, too. Jelena Jankovic won her 500th career match with a straight sets win over Eugenie Bouchard. "In order to have 500 wins, I think you have to have a pretty long career, be pretty consistent," the 28-year-old Jankovic said.

Jankovic will face Switzerland's Stephanie Voegele in the semifinals. Voegele rallied from a set down to defeat second-seeded Carolina Wozniacki 3-6, 6-4, 6-3 and send the 2011 Family Circle winner up the road to Augusta National - she's scheduled to cheer on boyfriend Rory McIlroy at next week the Masters - earlier than planned.

The sisters were put in the unusual spot of doubling up when the rain postponed much of Thursday's schedule.

Venus Williams looked her most comfortable of the week against the power-hitting Keys. Williams had needed a third set to pull out both her previous matches and it looked as though it might happen again when Keys was a point away from moving in front 4-1 in the second set.

But Williams was able to rally to win five of the final six games, securing her second semifinal berth in four tournaments this year.

Venus Williams seemed to have her first match under control, ahead 6-2 and 3-0 in the second set. Lapchenko rallied to win seven of the next eight games while a chilly drizzle fell in the middle of the second set and took a 1-0 lead in the decisive set. That's when Williams again found her game and pulled away by winning six of the final seven games.

Venus Williams returned to clay-court action at the 2012 Family Circle after an absence of about two years on the surface. A bout with the autoimmune disease Sjogren's Syndrome kept her from the game for almost six months between the 2011 U.S. Open and the 2012 Sony Open. She reached the quarterfinals here a year ago, falling to Samantha Stosur to prevent an all-Williams semi that time.

Safarova, who lost to Serena Williams, 6-0, 6-1 in the 2012 finals, led in the opening set and had a point to go up 5-2. Instead, Williams rallied back from deuce and won the final four games to take the set.

Williams' big serves and power game smothered Safarova after that. Williams served a 106 mph ace to set up match point, then chased down Safarova's drop shot to take the match - and give herself a well-earned rest.

• Read more articles by PETE IACOBELLI

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