By Ann Liguori
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Let’s appreciate the sister act.

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Both Venus and Serena Williams played first round matches Tuesday at the US Open, a tournament that wouldn’t be the same without them. In fact, all of tennis wouldn’t be the same without these legendary sisters.

For Venus, it is her 18th US Open. She won back-to-back titles in 2000 and ’01. And it is her 72nd Grand Slam main draw appearance, which is a record in the Open era.

This is Serena’s 17th US Open, and she has won the event six times dating back to 1999. It’s her 65th Grand Slam main draw appearance.

What would tennis be, particularly, American tennis without them?

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On Tuesday, Venus needed two hours and 42 minutes in the late afternoon to dispose of Kateryna Kozlova, 6-2, 5-7, 6-4, and within an hour of her match ending, her younger sister, Serena, came out on the Arthur Ashe Stadium court and breezed past Ekaterina Makarova, 6-3, 6-3, under the lights.

To watch these amazing sisters on the court and to comprehend their incredible accomplishments on and off the court is to truly appreciate the rarity of two sisters achieving such success in sports for such a long period of time.

What these two sisters have accomplished in tennis is extraordinary. Between them, they have won 29 major championships in singles and 14 Grand Slam women’s doubles titles playing together, their most recent major double’s title coming at Wimbledon this year.

Venus, at 36 years of age, is the oldest player in the draw. The fact that she can continue to perform at such a high level while suffering with Sjogren’s syndrome, an autoimmune disorder that results in fatigue and joint pain, makes her career even more amazing.

Serena is 34-years old and has won nine of her major titles while in her 30s. Serena is the oldest top-ranked player in WTA history, as she is spending her 308th and 309th weeks atop the rankings.

During this fortnight, Serena is hoping to win her 23rd major title in singles, and Venus is playing for her 8th major singles championship.

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Their accomplishments go on and on. In fact, the packet of information from the media center on these two sister superstars is as thick as an encyclopedia.

And let’s not forget their performances representing the U.S. in Olympic play. You didn’t hear the Williams sister deliberating whether or not to travel to Rio.

Venus won the gold in singles in 2000 and in doubles in 2000, 2008 and in 2012. And she brought home the silver medal this year in Rio in mixed doubles.

Serena won gold in doubles in the 2000, 2008 and 2012 Olympics and a gold medal in singles in the 2012 Olympics.

Off the court, they have fascinating businesses and projects and strive to continue educating themselves.

Venus owns fashion and interior design companies and wears her own designs on the court, a line of fitness clothing called “EleVen by Venus Williams.”

Serena’s fashion line is called “Aneres” (her first name spelled backward), and she has a signature line of handbags and jewelry sold on the Home Shopping Network.

They are also part owners of the Miami Dolphins.

Both sisters are very charitable. The Serena Williams Foundation helps underprivileged children.

In the history of sports, there have been other sibling superstars, including Maurice and Henry Richard, both Montreal Canadian legends who won 19 Stanley Cup championships between them. We had Reggie and Cheryl Miller — Reggie was one of the top shooters in NBA history, and Cheryl was one of the best female players in basketball. And of course, the Manning brothers in the NFL — Peyton and Eli. And the Bryan twins in tennis — Bob and Mike — have won over 100 doubles titles.

But Serena continues to dominate her sport, striving to set even more records. And Venus has enjoyed a bit of a resurgence on the court and continues to fight for equal prize money and other causes off the court. Together, they are a power “sister act” and arguably the most accomplished siblings in the history of sports.

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