Serena Williams hugs Venus Williams after defeating her during their women’s-singles quarterfinals match on day 9 of the 2015 U.S. Open at the USTA Billie Jean King National Tennis Center in New York City Sept. 8, 2015.
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Serena and Venus Williams have played against each other 27 times in their career. And they've never wavered against each other. On Tuesday Serena, who is trying to claim a grand slam—winning the Australian Open, the French Open, Wimbledon and the U.S. Open in the same year—beat Venus at the U.S. Open. But Tuesday's win, like all the others, did not break their sisterly bond.

At the end of the match, Serena had only positive words for her sister.

"She's the toughest player I've ever played in my life and the best person I know," Serena said.

Serena also took to her Instagram account and posted a touching tribute to her big sister. 

"She has my heart," Serena said of Venus. "Memories make my heart filled with more joy than I can express. A lifetime with @venuswilliams will not be enough."

Venus and Serena are great role models not only as athletes but also as family.