- Serena and Venus Williams both won at the Australian Open Monday
- It's the first time they're into the last eight together at a major since 2010
- They'll meet in the semifinals if they win their quarterfinals
(CNN)It could be a family affair for the Williams sisters at the Australian Open.
If Serena and Venus Williams -- who have combined to tally 25 majors -- both win their quarterfinals Wednesday, they'll meet at a grand slam for the first time since the Wimbledon final in 2009.
But Monday was already a day of 'firsts' for Venus Williams, whose career has been hindered by the autoimmune disorder Sjogren's Syndrome.
When the 34-year-old beat sixth-seed Agnieszka Radwanska 6-3 2-6 6-1, she ensured a quarterfinal berth at a grand slam for the first time in five years. Further it was her first top-10 win at a major since downing Italy's Francesca Schiavone at the 2010 U.S. Open.
"Of course, I want to be playing deep in all my events," Venus Williams told reporters. "Everybody wants that. But it really just doesn't happen every time for everyone.
"Now is my moment and I want to keep this moment going all year and then next year, too. That will take work."
But reaching the quarterfinals in Melbourne won't be enough for her. She still has the game and belief, she said, to go even deeper.
"I feel like I've been here before, so it's not like I'm jumping up and down for joy, 'Oh, shoot, what is this? I've never done this,'" she continued. "Yes, I've done this. This is what I'm always going into each tournament thinking I want to do, even when I fall short.
"It's definitely not the first time. I guess that's how I feel."
Serena Williams cheered on her sibling from the players' box during the victory over Radwanska and said following her own win over Garbine Muguruza that she was still inspired by Venus.
"She's a big influence, obviously," said Serena. "The way she's playing, her confidence exudes and permeates to me. It's a really good feeling."