World number one Serena Williams, seeking a third consecutive Miami crown and record eighth title at the hardcourt event, hammered Russian Svetlana Kuznetsova 6-2 6-3 while 16th-seeded elder sister Venus defeated fourth seed Caroline Wozniacki 6-3 7-6 (7/1).
Between them, the Williams sisters have won the Miami singles title 10 times. The only players to win the crown three years in a row are Serena, from 2002-2004, and Steffi Graf, who did it from 1994 to 1996.
Serena, 33, took 73 minutes in beating 2006 Miami champion Kuznetsova, improving her overall Miami record to 70-7.
“I don’t think I’m cruising,” Serena Williams said. “I have my matches and I’m really focused in my matches because all these players I play are really good.
“When Venus is playing before me I’m always excited to see her results and hopefully (see) a win. But I don’t usually watch her match because I’m trying to focus on mine.”
Serena could face her sister in the finals. While Venus, who suffers from the chronic medical condition Sjogren’s syndrome, has struggled in recent seasons, she has played well in 2015, winning her 46th career title in January at Auckland and making a run to the Australian Open quarter-finals, her deepest at a Grand Slam event since the 2010 US Open semi-finals.
“She’s playing really well, she’s playing really aggressive,” Serena Williams said of her sister. “I have always said what Venus has gone through has really motivated me.”
Venus Williams, 34, is playing her home event for the 16th time and owns three titles. The American took the win despite 37 unforced errors in a match riddled with a dozen breaks of serve. Williams has never lost to former number one Wozniacki, now 7-0 against the Dane.
“I’m persistent. I don’t give up and I believe in myself no matter what the odds are and what you may experience,” Venus Williams said. “I’ve always seen it as something to overcome and not something that could stop me.
“Having that perspective of glass half full helped me a lot.”
Spanish 12th seed Carla Suarez Navarro upset seventh seed Agnieszka Radwanska 5-7, 6-0, 6-4 and will be the next to play Venus Williams.