A brother or sister can help alleviate stress of tour life

The life of a professional tennis player can be a lonely existence.

So, for the likes of the Bryan brothers, having a sibling along for the ride as you hit a new city every week can make a huge difference.

Mike Bryan and his twin Bob have been on the road for the best part of two decades, racking up 16 Grand Slam titles en route to becoming the dominant force in men's doubles.

As siblings, they're not that unusual on a circuit that includes multiple Grand Slam winners Venus and Serena Williams among 10 sets of brothers and sisters in the main singles draws at this year's Australian Open.

"I think that's why we're still doing what we're doing," Mike Bryan said on Saturday.

"It's fun to have a companion out on the road, especially when you're traveling. There's a lot of time alone in hotel rooms, so a lot of times we're there playing games.

"Just to have your twin brother who is your best friend there, it's really kept us going for 19 years."

The twins sailed into the fourth round under sunny skies on a packed Showcourt 3 on Saturday, having prevailed over Germany's Mischa Zverev and Serbia's Nenad Zimonjic.

Zverev and his brother Alexander are also close, even though separated in age by a decade. They became the first brothers to reach the third round of the same Grand Slam in singles since Byron and Wayne Black in 1998.

With Mischa having secured his advancement with a stunning upset of world No 1 Andy Murray, his 19-year-old brother was losing a titanic five-set struggle with ninth seed Rafa Nadal at Rod Laver Arena.

Murray, meanwhile, was able to hang out with his brother Jamie at Melbourne Park until the older sibling crashed out of the doubles with partner Bruno Soares of Brazil.

Competitive nature

Unlike the Bryans and the Williams sisters, the Murrays do not have the complication of playing together, which can create a few challenges, according to Mike Bryan.

"When it starts going well, we're moving so strong, and moving like a unit. But when it starts going sour, it can be tough to get it back," the 38-year-old said.

"When your brother is not playing well, you can see him struggling, you can empathize, it's like a piece of you is playing bad. I think the lows are a little bit lower just to see your twin so down."

The Bryans are not the only set of twins on the circuit, with Czechs Karolina and Kristyna Pliskova this week becoming the first to reach the third round of a singles draw Grand Slam.

"For our parents it's perfect that they have both twins in the Grand Slam and now in the third round, which I think is for the first time so it's special," Kristyna said before she was felled by world No 1 Angelique Kerber.

"She's almost all the time with me so it helps," she said of world No 5 Karolina.

"She can give me some advice, we can talk about everything."

The world No 58 was unsure whether both sisters being good players has helped drive the twins to greater heights in the game than they might otherwise have attained.

"Maybe it's just nature?" she said.

The Pliskovas were fortunate enough to end up in different halves of the draw at Melbourne Park. For siblings, having to play against a brother or sister at a tournament can be complicated.

Juergen, the older of Austria's Melzer brothers, called his straight set win over brother Gerald in Wimbledon qualifying two years ago "the worst tennis day" of his life.

The 27 meetings between Serena and Venus Williams, who have both been world No 1 and own 29 Grand Slam singles titles between them, have often disappointed.

When they combine in women's doubles, though, they are an intimidating force and Venus was at something of a loss when asked whether her experience echoed that of Mike Bryan of the "lows being lower".

"We don't really lose that often," she said. "There haven't been a lot of lows."

Bob Bryan (left) and his brother Mike celebrate defeating Australia's Lleyton Hewitt and John Peers in their Davis Cup doubles match in Melbourne, last March. The American twins have racked up 16 Grand Slam victories in their career. AP File