Serena Williams has set up a third-round showdown at the US Open against her older sister after hitting 13 aces and overwhelming 101st-ranked Carina Witthoeft of Germany 6-2 6-2 in a little more than an hour.
Venus Williams advanced with a straight-set victory earlier on Wednesday.
This Williams vs. Williams matchup will be the earliest they’ve faced each other at a grand slam tournament in 20 years.
Serena leads Venus 17-12 overall and 15-10 at majors.
Two-time champion Venus beat Italy’s Camila Giorgi 6-4 7-5.
Venus, seeded 16th, powered through the first set but appeared to lose energy toward the end of the second in broiling conditions inside the newly built Louis Armstrong Stadium.
She said the crowd’s encouragement had helped her.
“I felt the energy, definitely,” Venus said. “That love-40 game at four all was not looking good and you guys really got me through that.”
Defending champion Sloane Stephens avoided an early exit, recovering from a set down to defeat Ukrainian qualifier Anhelina Kalinina 4-6 7-5 6-2.
Kalinina, 21, was the runner-up in the girls’ singles in 2014 and was playing in her first senior grand slam tournament after coming through qualifying.
She took advantage of errors from Stephens to win the first set and then fought back from 4-1 down in the second set to level at 5-5 but the American held firm to win her ninth successive match at Flushing Meadows.
The third-seed fired an ace on match point to complete the comeback, which took two hours and 46 minutes on a hot and humid day on Arthur Ashe Stadium.
“I wasn’t playing my best,” the 25-year-old said.
“It was super hot and that was no fun at all. I was sweating a lot,” she added. “But I came out in the third set bouncing around.”
Other seeded winners on the women’s side included No. 8 Elina Svitolina, No.15 Elise Mertens, No 19 Anastasija Sevastova and No.23 Barbora Strycova, all in straight sets.