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Venus Williams (R) and Serena Williams (L) of the United States return a shot against Ekaterina Makarova and Elena Vesnina of Russia during their women's doubles quarterfinal match on Day Nine of the 2014 US Open at the USTA Billie Jean King National Tennis Center on September 2, 2014 in the Flushing neighborhood of the Queens borough of New York City.
Elsa—Getty Images

Sisters Venus and Serena Williams have a long and storied rivalry on the court. Practice partners since they were toddlers, the two have met more than two-dozen times on the professional circuit. On Tuesday night, Serena and Venus Williams will face each other in the quarterfinals of the U.S. Open with Venus as Serena’s biggest obstacle to achieving the calendar Grand Slam.

Ahead of the match-up, here are a few facts you may not have known about the Williams women:

Venus and Serena have played 26 times on the professional circuit

Serena leads 15-11 in these match-ups

The sisters have played eight Grand Slam finals against one another

Serena won six of them

Venus is the only person to beat Serena twice in the U.S. Open

In 2001 and 2005

Venus has a faster serve

Venus holds the record for second fastest serve in the history of women’s tennis at 129 mph, while Serena places third with 128.6 mph

Each sister has won four gold medals in the Olympics

The two have teamed up for three doubles gold medals, and each has a singles win as well

They largely stayed off the Juniors’ Tennis Circuit

Their father and coach, Richard Williams, focused on training the girls in Florida rather than on having them compete when they were young, which gave them the advantage of being better-rested than their competitors

They shared a house in Palm Beach Gardens, Fla., for 15-plus years

The women, now in their 30s, moved into separate complexes in 2014, about 5 miles apart

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Write to Eliana Dockterman at eliana.dockterman@time.com.

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