Serena and Venus Williams, once considered one entity, find themselves headed in different directions, even as their paths collide at the 2015 U.S. Open.
Serena defeated Madison Keys (6-3, 6-3) and Venus beat Anett Kontaveit (6-2, 6-1) in the fourth round to set up an all-Williams quarterfinal showdown Tuesday.
"It's been awesome to have such a great sibling rivalry with Serena. We are proud of each other. We inspire each other," Venus told the crowd at Arthur Ashe Stadium during her post-match interview.
Serena leads the head-to-head series 15-11. The last time Venus defeated Serena was at the Rogers Cup in Montreal last year. Venus won four of their first five matches. Serena has won six of the last seven.
Throughout much of their lives, they've been talked about as if they came as a pair. Venus and Serena, or the Williams sisters, is how they are often spoken of.
Now in their mid-30s, the sisters remain as close as ever and supportive of each other. However, they've grown up, and the two, once an inseparable duo, lead increasingly separate lives.
These days, it seems as if Serena is photographed with friend Caroline Wozniacki more than she is with Venus.
Last year, Venus and Serena seemed to be preparing to leave the home they shared for 15 years in Palm Beach Gardens, Florida, and move into two separate residences five miles apart.
Serena told the Independent's Paul Newman that she is "finally moving away from my sister after 34 or 35 years by the time it's done...It's a good time. I figure that will be my new life. Of course we will live down the street from one another. It will be a new start...I'm kind of scared, but I'm growing up."
They recently sold a midtown Manhattan loft they shared for $2.1 million to NFL independent investigator Ted Wells.
The two haven't played doubles on the tour since their bizarre exit from Wimbledon in 2014. They were scheduled to play at Wimbledon this year but withdrew before their first scheduled match.
It's part of the maturation process. Even the Bryan brothers, both married now, had to get their own homes.
Indeed, the sisters appear to be laying the groundwork for post-playing days.
Serena, who long expressed an interest in acting, landed a small part in the movie Pixels. She's also increased her endorsements haul during her run of Slams. Over the past year, she's added Australian lingerie line Berlei and JPMorgan Chase to her list of endorsement deals.
Meanwhile, Venus, 35, the oldest woman in the draw, has been building a business empire focused on ownership instead of endorsements. Venus owns a clothing line, EleVen, a few Jamba Juice franchises and still finds time to operate V Starr Interiors, a commercial and residential interior design firm. She and Serena also have a limited stake in the Miami Dolphins.
Last month, in the middle of preparation for the U.S. Open, Venus picked up a bachelor's degree in business administration from the University of Indiana East.
Her New York Times best-selling book Come to Win: Business Leaders, Artists, Doctors, and Other Visionaries on How Sports Can Help You Top Your Profession is about business, not tennis.
Although they arrived on the tennis scene as a unit, they have always been distinguishable. Venus, with a long, lanky build like her father, has her mother's calm demeanor and measured temperament. Serena, who inherited her mother's curvaceous figure, has her father's more volatile personality.
While both have amazing serves, Serena's second serve is more reliable, and her overall game has always been more fundamentally sound.
When they play Tuesday, it will mark their 27th meeting. With so much on the line for Serena, it's hard to imagine the emotions each will feel when they take the court.
They've come a long way from their first professional match, a second-round meeting at the 1998 Australian Open.
Venus, 17 at the time, defeated Serena. After the match, she spoke with the Los Angeles Times' Julie Cart about how odd it was to play her sister.
"I feel good that I won. ... Even though it was Serena, I'm still a competitor. After the match I told her, 'Serena, I'm sorry I took you out. I didn't want to, but I had to do it.'"
Here we are, 17 years later, and in some ways everything has changed, but in others, it's all the same. Serena and Venus square off again. Just like it was half their lives ago. But these days, Serena sits atop the tennis tower, with Venus (ranked 23rd in the world) an afterthought in comparison.
There's an analogy somewhere for this match. It lives in the land between an epic clash and ships passing in the night. Perhaps we won't have an apt one until the winning sister bellows her victorious scream.
Serena told espnW.com's Melissa Isaacson that she could only guarantee fans at Arthur Ashe Stadium one thing when it comes to Tuesday's showdown: "At least a Williams will be in the semis, so that's good."