Venus and Serena Williams
Serena Williams hugs Venus Williams after her loss to her sister during Day 8 of BNP Paribas Open on March 12, 2018, in Indian Wells, California. Kevork Djansezian/Getty Images

World number one Roger Federer heaped praise on Serena and Venus Williams as he looked back on their legacies in tennis.

The duo are arguably the most successful siblings in sports today with Serena, 36, boasting 23 Grand Slam titles, having last won the 2017 Australian Open, while Venus, 37, has 14 to her name having last won at Wimbledon in 2016.

With the latter making two Grand Slam finals last year, the sisters continued to remain at the top level even in their mid-thirties and Federer, who is experiencing success at 36 years of age himself, believes they have lived up to their hype from when they arrived on the tennis scene.

Roger Federer and Serena Williams
Roger Federer and Serena Williams have dominated their respective circuits in tennis for over a decade. Getty

“Longevity and dominance. They showed that,” Federer said, as quoted on Sport 360. “They had a massive arrival on the scene, a lot of buzz around them, and they lived up to the hype. Came out and crushed it."

“From the very beginning, they were very interesting to follow. I think they hardly played any juniors, really, which made it more of a mystery, because you just didn’t know exactly what to expect from them. And coming from being coached by their dad. I mean, it’s an incredible fascinating story,” he added.

Venus and Serena faced each other on Monday for the 29th time in the third round at Indian Wells with the former breaking a three-match losing run against her sister to emerge victorious in a 6-3, 6-4 win.

Serena was notably featuring in her first competitive event since her Australian Open win and pregnancy that followed, but along with her sister, has had to deal with health issues and injuries in the past.

Federer, who experienced a career resurgence last year after a long injury lay-off, is happy to see them still thriving and believes Serena can emulate him by having her comeback from pregnancy be the story of the year.

“For many years we were worried that they were going to check out early with sickness or injuries,” Federer added. “We weren’t sure if they’re going to play as long as we hoped them to play. And here we are. They are both over 35, 36, and still basically playing at the top. Serena being a mum now, Venus overcame a lot of also difficult situations and still playing."

“Being older again than Serena, myself, it’s wonderful to see and I’m very happy for them, especially now watching Serena’s comeback since the baby. I think that’s going to be a huge story, maybe the story of the year. Hopefully she decides to play a lot and enjoy herself in the process and get back to who knows how high? It almost doesn’t matter, but it would just be amazing to see her do it now."

Venus will meet Latvia's Anastasija Sevastova in the round of 16 next on Tuesday.