Almost everywhere you looked on Daniel Island on Friday, there was a Williams sister.

Serena leads, 13-10

Last five:

Year Event Round Winner

2009 Tour Championships 1 Serena, 5-7, 6-4, 7-6

2009 Tour Championships F Serena, 6-2, 7-6

2009 Wimbledon F Serena, 7-6, 6-2

2009 Miami S Serena, 6-4, 3-6, 6-3

2009 Dubai S Venus, 5-7, 6-1, 6-0

Go to our Family Circle Cup page for more coverage.

Venus riding on a golf cart to Billie Jean King Court. Serena hitting balls toward the kids in the second level holding the “We Love Serena” sign. Both veterans handling the best stuff America’s rising young stars could throw at them.

From before 11 a.m until almost 7 p.m., Family Circle Cup fans reveled in an unprecedented four straight matches of Venus and Serena, nine sets and almost six hours of the most famous sister act in pro sports.

“For the record, we’ve never both played two matches in one day,” Serena told the appreciative crowd after her second match, a 6-4, 6-1 quarterfinal takedown of No. 6 seed Lucie Safarova. “You guys had a real treat!”

And there’s more to come. No. 1-ranked Serena and No. 24 Venus will meet in today’s 1 p.m. semifinals (on ESPN2), the 24th time the sisters have met as professional tennis players. Serena leads the series, 13-10, and has won the last four matches.

“She’s my toughest opponent I’ve ever played,” Serena said of Venus.

How cool was the daylong Williams-palooza?

Madison Keys sounded like she wished she was one of the 8,012 fans in the stands. Instead, the 18-year-old was on court, dropping a 6-4, 6-4 decision to Venus in the quarterfinals.

“Today was one of the best days to have a ticket,” Keys said. “You get to see Venus and Serena play four times in one day.”

Said Serena: “It was a pretty awesome, a pretty intense schedule.”

Rain played havoc with Thursday’s order of play, with only four matches completed. That meant Venus and Serena both faced double-duty on Friday. And tournament officials made up for the rain day with the double-take slate of Venus, Serena, Venus and Serena.

“I was thinking, ‘It’s a quadrupleheader today,’” said Venus, who opened the day with a 6-2, 4-6, 6-2 win over American Varvara Lepchenko. “Hopefully, that was a lot of fun for the fans. I don’t know if that will ever happen again. I hope it doesn’t.

“But it was a really cool thing for the tournament to do, to reward the crowd for hanging in there through the weather.”

Serena fell behind, 4-2, against Safarova, who had a break point for 5-2. But after watching 32-year-old Venus, who has struggled to deal with an autoimmune disease the last few years, win two matches, Serena wasn’t about to lose.

“It was really motivating for Venus to win today,” said Serena, who took out American qualifier Mallory Burdette, 6-4, 6-2, in her first match. “I figured if she can win two matches, I have no excuse not to win my two matches.”

The four Friday wins set up the latest chapter in the most emotionally fraught rivalry in tennis in today’s semis. The sisters have not met since 2009, when Serena beat Venus in the finals at Wimbledon. Venus’ last win came in three sets, also in 2009, in the Dubai semifinals.

“I don’t love playing her,” said Serena. “If I win, I’m not super excited, and if I lose, I’m really not excited.”

But Serena, 31, did say the matches with Venus have gotten easier to handle since they first played in 1998 at the Australian Open (Venus won in straight sets).

“I look at it as playing a great champion,” Serena said. “She’s won so many Grand Slams (seven in singles), so you know it’s not going to be easy.”

Serena is seeking her third FCC title and second in a row. Venus, the 2004 champion, is trying to match her sister’s total. Only one of them will make it to Sunday’s final.

“We just both want to win,” Venus said. “I think we just have so much respect for each other’ game that it makes it a little tougher, because you know you are not going to get an easy win. You know you have to be on your game and play well every single time. I think that’s the toughest part.”