If Serena Williams would feel sympathy for any opponent standing in the way of her pursuit of tennis’ first true Grand Slam in 27 years, it might very well be her sister Venus.

Still, no way was Serena going to let anyone, or anything, stop her on this night, even if she found herself in a mid-match lull while facing her older sibling in the U.S. Open quarterfinals. Moving two matches from history, top-seeded Serena got all she could handle from 23rd-seeded Venus before moving onto the semifinals at Flushing Meadows with a 6-2, 1-6, 6-3 victory Tuesday in the 27th installment of the unique Williams vs. Williams rivalry.