"I am very happy for her that she is doing well," says Agnieszka. "She is working really hard for that, she has been through a lot of things and I am happy that she has made the top 30 already.
"Hopefully, I'll see her in the top 10 very soon -- there's a big chance."
Much like Serena and Venus, the Poles were first taught by their father -- although in contrast to Richard Williams, Robert Radwanska did have a coaching background prior to his daughters' births.
Those searching for differences can point to Agnieszka's birthplace of Krakow differing to Urszula's in Gronau, since her father was then working in the north-western German town as the local tennis pro.
His profession meant the girls were surrounded by tennis from birth, with early images showing the sisters in the midst of bats and balls -- and one memorable picture showing them tottering around like ballerinas, albeit with their feet squeezed into tennis ball canisters.
Their father coached Aga and Urszula from the ages of 5 and 4 respectively but he stopped traveling last year, and both are now working with Borna Bikic (Jelena Dokic's former coach) as well as Polish Fed Cup coach Tomasz Wiktorowski.
Nonetheless, Robert still trains his girls whenever they go home to Krakow.
"This is our home so we love coming back," says Urszula of Poland's second largest city. "Our family is here but it's good that I have a sister so I can always practice with her. I don't have to find a hitting partner and also our coach is our dad, so it's perfect."
The historic city is by no means perfect for the tennis professionals -- it has no hard court, for example -- but its enduring appeal for the girls more than makes up for that.
"It's always a great feeling to be here, especially since we are traveling 10 months a year," says Aga. "Even if I can only go home for two days, I will as it's always nice to just sit on my couch, watch TV and be in my kitchen. Those two days make a huge difference -- it feels like I have a normal life."
For the rest of the year, the sisters are largely on the road -- sometimes together, sometimes not -- and they always find a way of staying in contact.
"When something's happened to me, Aga is the first to know," says Urszula. "We talk to each other all the time -- on Skype, over the phone, texting. We are always in touch."
More often than not, they are normally in the same place -- and not just playing singles, but also teaming up for doubles together.
In London last year, where Agnieska was honored to be Poland's Olympic flag bearer, they had mixed fortunes, exiting the Games in the second round before withdrawing from the third round at Wimbledon to help Aga, suffering from illness, in her singles bid.
With a WTA doubles title already to their name, at Istanbul in 2007, the next step is to join the select band of sisters to have won a grand slam doubles title -- with the Williams and Roosevelts joined only by Ukrainians Alona and Kateryna Bondarenko in the history books.
Even if they fail, one thing is for sure -- that the Radwanska sisters are inspiring the next generation of Polish tennis players.
"I can clearly see that tennis in Poland is getting better. A lot of kids are trying to play right now and trying to be professionals -- so it's nice to see that -- and people are talking more about tennis so it's becoming more popular," says Urszula.
"And when I see Aga having great results, I want to be the same or even better."