Serena and Venus Williams advanced to the quarter-finals of the ATP and WTA Miami Open on Monday, the sisters each cruising to a straight-set triumph. 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.