MELBOURNE, Australia — The Williams sisters held court at the Australian Open on Thursday, a back-to-back Venus-Serena doubleheader that left the siblings still in the mix for yet another Grand Slam singles title.

Serena Williams, the Australian Open defending champion who has 11 major singles titles, beat Petra Kvitova of the Czech Republic 6-2, 6-1. Venus, who has seven, defeated Austrian Sybille Bammer 6-2, 7-5.

Top-seeded Roger Federer beat Victor Hanescu 6-2, 6-3, 6-2 in a night match at Rod Laver Arena attended by Prince William, second in line to the British throne.

Federer lost last year's Australian final to Rafael Nadal, who plays his third-round match on Friday.

Federer acknowledged Prince William in the crowd after the match.

"Your Royal Highness, welcome to the world of tennis. Thanks for coming," Federer said.

Venus preceded her sister at Hisense Arena with the roof open under a warm, sunny Melbourne afternoon that morphed into an early evening sky streaked by twilight.

Only one Williams can make it through to the final on Jan. 30 — they are drawn to face each other in the semifinals if they advance that far. The way they played Thursday, it's a good chance they will.

Serena, who has won the Australian Open every odd-numbered year since 2003, was more dominant, completing her match in just over an hour and converting four of her 11 break-point chances.

"I feel if I play well, I can beat anybody," Serena Williams said.

Serena didn't know how her sister was doing before she went on court.

"No, I didn't watch Venus," Serena said. "I can't really watch her on TV, and definitely not before I play. I get way too nervous."

Venus Williams, who has been to the final at Melbourne Park just once, when she lost to her sister in 2003, spent about 30 minutes more on court to beat Bammer. She faced her second left-hander in a row — she beat Lucie Safarova in the first round.

"Playing two lefties in the first two rounds is little unusual, but I was up for the challenge," Venus said. "Her game is a little bit different from most people, so really have to be a little more patient because she's kind of hitting a kind of a moonball almost. I just had to just make sure I stayed on my rhythm."

Ana Ivanovic, the 2008 Australian Open finalist and French Open winner the same year, never found her rhythm. She extended her run of poor results in a second-round 6-7 (6), 7-5, 6-4 loss to Gisela Dulko of Argentina.

Since her French Open win, she has failed to get past the fourth round of a major six times.

Ivanovic says she's still a work in progress and is probably playing better than in 2008, when she attained the No. 1 ranking. Personal pressure might be the difference.

"I think it's expectations from myself that I put," Ivanovic said. "Actually, I think I'm striking the ball better now than I did in 2008 or any previous years. My movement is getting there. It will take some time."

U.S. Open finalist Caroline Wozniacki of Denmark advanced 6-3, 6-1 over Julia Goerges of Germany and will next play No. 29 Shahar Peer of Israel, who beat Tsvetana Pironkova of Bulgaria 6-1, 6-4.

Wozniacki could play Venus Williams in the quarterfinals.

"I think she has the potential ... the sky's the limit," Williams said of Wozniacki. "Obviously if we both play well enough, it could happen."

Other women advancing were No. 7 Victoria Azarenka of Belarus, No. 9 Vera Zvonareva of Russia, No. 10 Agnieszka Radwanska, No. 16 Li Na of China and No. 32 Carla Suarez Navarro of Spain.

In men's matches, Djokovic had a slow start against Swiss journeyman Marco Chiudinelli before advancing 3-6, 6-1, 6-1, 6-3.

No. 9 Fernando Verdasco, who played the longest match in the tournament's history before losing to fellow Spaniard Nadal in the semifinals last year, advanced to the third round with a 6-1, 6-2, 6-2 win over Ivan Sergeyev of Ukraine. No. 10 Jo-Wilfried Tsonga, who lost the 2008 final to Djokovic, had a 6-4, 6-3, 6-3 win over American Taylor Dent.

"This court is most special because I won my only Grand Slam here," the 22-year-old Djokovic said of Rod Laver Arena, where he beat Federer in the semifinals en route to the 2008 title. "It has the nicest possible memories."

Djokovic will next play Uzbekistan's Denis Istomin, who beat Michael Berrer of Germany 7-5, 6-3, 6-4.

Sixth-seeded Nikolay Davydenko had a 6-3, 6-3, 6-0 win over Ukraine qualifier Illya Marchenko. Marcos Baghdatis, the 2006 finalist, struggled with cramping late in his match but held on to beat No. 17 David Ferrer of Spain 4-6, 3-6, 7-6 (4), 6-3, 6-1.

Baghdatis will face former No. 1-ranked Lleyton Hewitt, who had a 7-6 (3), 6-4, 6-1 win over American Donald Young. The last Hewitt-Baghdatis match at Melbourne Park was a third-rounder that finished at 4:34 a.m. in 2008.

"It was sort of epic in the locker room before we went on the court as well," Hewitt recalled Thursday of the lengthy match. "We both warmed up and kept getting told we were going to be the next match on.

"It was just a weird situation for both of us to be in. Then to go five sets like it did, it just added to the drama."