Bidding for their 14th Grand Slam doubles title, but first at Flushing Meadows since 2009, the siblings beat seventh-seeded Timea Babos and Kristina Mladenovic 7-6 (0), 6-7 (4), 6-1 on Thursday in the first round.
On July 1, in the second round of Wimbledon doubles, Serena looked disoriented during warmups, having trouble grabbing tennis balls tossed to her by ballkids. After four consecutive double-faults in one game, she quit. The reason given was that she was ill.
Both Williams sisters are into the third round of singles at the US Open this year.