WIMBLEDON, England - It's hard enough to play a sibling on a neighborhood tennis court, let alone Centre Court at Wimbledon.
But that could be the fate that awaits Serena and Venus Williams this week, as tennis' serve-and-volley, grass-court show moves toward a final act.
Wimbledon resumes with today's round of 16, and all eyes in the tennis world will be on the Williams sisters.
They haven't played well yet, haven't unleashed their superb all-court games, but remain on course to meet in Saturday's women's final.
In a tournament as unpredictable as this year's Wimbledon, the Williams sisters just might be the only two near-sure things.
Could anyone at the outset predict a Wimbledon as weirdly wonderful as this?
Fourteen of the top 16 men's seeds were beaten in the first week, the American men erased, and the flagging careers of Richard Krajicek and Mark Philippoussis revived in time for their surprising meeting in today's fourth round.
Maybe Wimbledon will end with Australia's Lleyton Hewitt confirming his status as the world's No. 1 player or No. 4 Tim Henman and Greg Rusedski advancing to a stunning all-British men's final.
The women have been more predictable, with a yawning gap between the rest of the pack and the top three players - the Williams sisters and Jennifer Capriati.
Perhaps that gap will close this week.
The round of 16 should present the Williamses with their first significant tests of the tournament. No. 1 Venus Williams, the two-time Wimbledon champion, faces No. 16 Lisa Raymond, a steady grass-court performer. No. 2 Serena Williams faces a tricky match against Chanda Rubin.
The main events, though, seem to be shaping up in the projected semifinals, where Serena Williams could face Capriati and Venus Williams could face last year's losing finalist, No. 6 Justine Henin of Belgium.
But here's the larger problem for women's tennis. What if the Williams sisters get to another final and can't fire up themselves or the crowd?
Great tennis is often built around great rivalries swirling with fiery personalities and tennis conflict. Chris Evert vs. Martina Navratilova and John McEnroe vs. Jimmy Connors were two of the best. Evert-Navratilova simply played great tennis - crowds could get behind one player or another. McEnroe and Connors fed off mutual hatred and contrasting talents.
The Williams sisters surely have different personalities and playing styles - Venus, 22, seemingly more reflective, the bigger server, Serena, 20, displaying more flair, whether by wearing a tiara on court or lashing a forehand.
But they don't seem to have much of a rivalry, as sisters or players.
After growing up together, practicing together and climbing to the top ranks of women's tennis together, they still haven't figured out how to play a passionate final together.
Maybe it will happen here. Maybe at the U.S. Open.
But for now, all tennis can go on is past performance, and past performance isn't so wonderful, with Venus holding a 5-3 edge against her younger sister, including a straight-sets victory at the 2000 Wimbledon semifinals. But Serena has won three of their past four matches, including a tepid French Open final.
At least they've dispelled a perception that their matches have a prearranged quality overseen by their father, Richard Williams.
"Well, obviously that has never happened in the past," Serena Williams said. "We never discussed who is going to win. If so, I should have at least won a few more Grand Slams than Venus. I mean, really. It took me forever to win another one. For a while, just up until a couple of weeks ago or months ago, she had just this command on me. Every time we played, she would beat me."
Yet even as she talks of wanting to win a title, Serena Williams can't help lauding her sister, adding: "Venus is playing great here. And she's serving unbelievable."
Other players say they can understand the problems faced by the Williams sisters.
"I couldn't imagine playing against my own brother," Capriati said. "You know, the nerves. And I don't know how mentally you can just go out there and play against your own blood. And so it just seems like they're not playing their best tennis at the same time. And maybe that's nerves."
Belgium's Olivier Rochus defeated his brother, Christophe, in the opening round and said it was a terrible thing.
"You can't go like this," he said, pumping his fist, acknowledging all the emotion was drained out of a match of siblings.
Others, though, sense the Williamses will find a way to play a great match. In a conference call last week, Evert said Venus Williams will have the edge at Wimbledon because she will try hard to come back from the defeat at the French Open.
"I think the older sister pride will definitely come into effect and help her win this title," Evert said.
Competition for titles and rankings may also propel the sisters and yield a rivalry.
"Both of them are talking about winning Grand Slams and both of them are talking about the desire to become No. 1 and we haven't heard this from Serena," Evert said. "We've only heard 1 and 2 before. It's hard for me to believe that they can still remain as close as they are if they both want to be No. 1 in the world and they both want to claw their way and win these Grand Slams.
"There's got to be some friction there. In competition, there's always friction. There's going to be some ill feelings somewhere along the way."
Love can spoil a rivalry. But a little sibling rivalry just might save women's tennis.
Lleyton Hewitt (1) vs. Mikhail Youzhny
Tim Henman (4) vs. Michel Kratochvil
Venus Williams (1) vs. Lisa Raymond (16)
Chanda Rubin vs. Serena Williams (2)
Eleni Daniilidou vs. Jennifer Capriati (3)