Just like old times.

Used to be that a match involving Miss Williams vs. Miss Williams, as they like to say at the All England Club, was a regular occurrence at the latter stages of the most prestigious tennis tournaments in the world.

During a span of eight majors from the U.S. Open in 2001 to Wimbledon in 2003, Serena and Venus Williams participated in six all-in-the-family Grand Slam finals. Think about it this way: Before that stretch, the only previous major title match between sisters came when Maud Watson beat her younger sibling, Lillian, in the very first Wimbledon women's final in 1884.

There would be two more all-Williams Grand Slam finals, both at Wimbledon, in 2008 and 2009. But since then, they have not met in any round at any Slam. Until now. No. 1-seeded Serena and No. 16-seeded Venus will reprise their unique rivalry on Monday in the fourth round at Wimbledon.

"We just don't know what can happen there. We've all seen, a million times, them play. And we've seen different results, especially at Wimbledon. You just have no clue," said Venus' coach, David Witt. "We've seen good matches. We've seen bad matches."

This will be their 26th showdown on tour (Serena leads 14-11), their 13th at a major (Serena leads 7-5), and their sixth at Wimbledon (Serena leads 3-2).

It comes 17 years after their first professional matchup, in the second round of the 1998 Australian Open.

And it comes 15 years after their first encounter at the All England Club, in the 2000 semifinals

"I think we're both more mature. Still as tenacious," said Venus, who won that one en route to the first of her seven career Grand Slam titles, five at Wimbledon. "I mean, back then, we were definitely fun to watch. I think we still are."

Serena also has won five trophies at the grass-court tournament, part of her collection of 20 major singles championships.

Her narrow escape in the third round Friday against Britain's Heather Watson — after trailing by two breaks at 3-0 in the third set, then twice standing two points from defeat at 5-4 — extended Serena's Grand Slam winning streak to 24 matches. She is aiming for a fourth consecutive major title, a self-styled "Serena Slam," and trying to get the third leg of a calendar-year Grand Slam.

Given that Venus is 35 and dealing with the day-to-day difficulties of an energy-sapping autoimmune disease, and Serena turns 34 in September, it seems fair to ask: How many more times will the world get to see this?

Remember, they were taught to play tennis by their father in Compton, California, and went on to spend time at No. 1 in the rankings, collect a total of 27 Grand Slam singles titles and another 13 as a team in doubles.

When they're across the net from each other, it can be awkward for everyone involved — the sisters themselves, of course, but also their parents, their sisters and even their coaches.

"It's fun, in the regard of seeing two of the best athletes in tennis play. ... But it's tough. It's tough watching. It's tough for them playing," Witt said. "When they do play each other, I just say, 'She's going to be your sister after the match. You've got to go out there and just play the ball. Forget about who's on the other side.'"

Said Serena's coach, Patrick Mouratoglou: "It's always super-special and difficult to play her sister, first because she's a super player — and even better on grass. And second, because it's her sister."

Asked which Williams fans will be pulling for, Venus said: "I'll probably be cheering for her."

Serena, meanwhile, predicted: "I expect more people to be rooting for Venus."

Really?

"I would be rooting for Venus," she said.

"I mean, she's been through so much. She's had a wonderful story. She's been so inspiring to me. You know, she's just an incredible individual. She's just so amazing," Serena added. "She's been so inspiring to a lot of people with the same things that she goes through, too."

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