“For the most part,” she said, “Venus would be on my dad’s court, Serena would be on my mom’s court, and we’d jump. It was like this rotating system.” All the sisters agree that Oracene’s court was the toughest. Richard liked to play games and goof, but their mother was all business and was matter-of-fact in her criticisms. “Even now,” Serena wrote in her book, Oracene is “one of the best at helping to break down my game.” In conversation, Isha points out that it’s always her mother who goes with Serena to the Australian Open, not her father. “And she’s won the Australian five times.”

Oracene did not grow up a Jehovah’s Witness. She belonged to a religious family in Michigan but lacked a church to attend in L.A. Some Witnesses came to her door one day, and she liked their message, with its emphasis on their strict interpretation of the Bible. In 1984, just as Venus and Serena were picking up rackets for the first time, Oracene was baptized and began raising her girls in the faith. Richard never did convert. He read some of the teachings, but he was not and is not a Witness. As much power as he possessed in the family, there remained a kind of inner circle — of women and faith — of which he remained outside, which may go some way toward explaining how the girls can both revere him and roll their eyes at him. He’s their father, but he’s other. Among themselves, the women in the family maintain what Oracene, quoting Colossians, calls “a perfect bond of union.” When I spoke with Lyndrea, the youngest of the three older girls (and perhaps the most unforcedly sweet of all the sisters; about Lyn, as they call her, there was nothing forbidding or closed), she was in the car on her way to the Kingdom Hall in Los Angeles to give a talk. And when I asked Isha if the girls ever went around house to house, the way Jehovah’s Witnesses do, she said yes, she had been “out in service” with Venus and Serena. “It’s a trip, too,” she said, “people be blown away.”

It’s impossible not to feel that this fierce closeness of the Williams women — strengthened by their shared faith, with its emphasis on separation from the world — has had not a little to do with the tremendous psychological stability Venus and Serena have demonstrated over the nearly 17 years of their careers. It’s amazing to think, but when this article was first in the planning stages, only a few months ago, it was conceived as a story that would mark the decline of their careers, the beginning of a conversation about their legacy. The word “retirement” had begun to appear in discussions of both sisters. This wasn’t writing them off; it just seemed like an accurate read of the situation. Venus found out she had Sjogren’s syndrome, an autoimmune disorder that often causes severe joint pain, among other symptoms. She’d fallen quite far back in the rankings, because of a lack of match play. The illness dogged her for years, until the doctors finally figured out what was wrong. It had been hard for her to accept that she was sick. “I spent my whole life playing sports and training and pushing myself to the limits,” she told me. “When you get told that you have a disease, it’s like: ‘Really? Nah, it’s all right. I don’t believe that. It must be something else, I’m just making an excuse, let me push harder.’ ” Serena, meanwhile, had cut a tendon in her foot with a piece of glass, requiring several operations, which led to a pulmonary embolism. She also suffered a giant hematoma, caused by one of the shots she took to prevent another embolism. Naturally their fitness suffered. It seemed, frankly, physically impossible that the sisters would ever regain the tip of the tennis pyramid. A good time to talk about what they had meant to the game, how they had changed it and been changed by it.

But last month, Serena won Wimbledon again. Then she won the Olympic gold medal in women’s singles. Then she and Venus (Venus actually playing slightly better than Serena, according to Serena) won gold in women’s doubles. The whole thing was a joke, a comedy. The Williams sisters were dominating tennis again. Serena, in her final match, machine-gunned her onetime rival Sharapova off the court so brusquely and efficiently, it looked as if she had an urgent appointment somewhere that she couldn’t miss. Venus, in closing out the gold-medal doubles match, hit what she felt was the best shot of her career. Her description of it in Cincinnati was beautiful (it can be hard to get tennis players to talk about their game in an analytical way). “I did a play that I normally don’t do,” she said. “Something moved my body.

“Serena was serving from the ad court, and I don’t really like to cross, to poach on the ad court, because I usually like to poach when I have a forehand. I’m thinking: I gotta help Serena out, because she always helps me on my serve. I’m not helping her enough.

“All this is going through my head. So my plan is like, I’m gonna go over, but I’m not gonna go too early; I don’t want [the other player] to see me. But this is all subconscious almost. The next thing I know, I’ve left. I don’t remember making my body move. I’m just hitting the shot. Now, I have a great one-handed backhand volley. But I hit it two-handed! I don’t know what happened. It was like watching myself from above when that happened, and like I feel like, this is the best shot of my whole life.”