Christos Kyrgios has returned serve at critics of his brother Nick over his behaviour at Wimbledon, saying his brother is a fantastic bloke and his critics are exaggerating his sins.

Overnight, Nick made it through to the third round in straight sets but was accused of belittling the chair umpire when a linesman reported him for swearing.

“The way he spoke to the umpire last night, I compare it to something Federer did a little while ago,” Christos told 7:30.

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“If the umpire’s saying to the player, ‘Don’t speak to me’ or ‘You can’t speak’, that’s not really a respectful way to speak to a player.

“So I think he was well within his rights to give something back to the umpire.”

Fairfax sports writer and author Peter FitzSimons, though, had a blunt warning for Nick.

“I’m not the arbiter of proper behaviour but to judge my Twitter feed, a hell of a lot of Australians say, ‘No, don’t do that. Please, we’ll make you a hero but don’t do the carry on. Don’t be a dickhead to ball boys, don’t be a dickhead to umpires, don’t bait the crowd. Play, just play’,” he said.

Christos said the criticism was over the top and his brother was not in danger of becoming a tennis brat.

“If arguing your point when there’s contention around the rules is being a brat then I guess I’m a bigger brat than Nick,” he said.

“You can either roll over when something doesn’t go your way if it should be going your way and take it, or you can argue your point and if arguing your point is being a brat then I’ve obviously had the wrong definition for many years.”

Christos is enjoying watching his brother play at Wimbledon and said he has never been prouder of him.

“He’s a great bloke. One of the best blokes I know. On court he’s fiery and on court he’s competitive but if he wasn’t that person he wouldn’t be where he is today,” he said.

“Off court – plenty of qualities – he’s always looking after charities, always about family, always about being a good person, always about inspiring others.”

Christos said his brother “loves” the support he gets from Australian fans.

He said the criticism of his famous brother came with the territory but the allegations against him had been exaggerated.

“I guess my mum gets upset and that sort of thing. He’s in the public eye so everything he does is going to be scrutinised,” he said.

“That’s fine as long as what’s being said is actually substantiated with what actually happened.”

FitzSimons says Nick risks alienating fans

Mr FitzSimons, though, who strongly criticised Nick in his column, said the player risked alienating his fans.

“Can’t we cut to the chase? You look at Lleyton Hewitt who – when he burst on the scene very similarly – was wonderfully talented, huge heart, chased down every ball,” he said.

“But for 10 years shouted at linesmen and you just go – as I wrote in the [Sydney Morning] Herald – ‘we want to love you, you’ve just got to give us a bit more to work with here and not look like a dickhead most of the time’.”

Andrew Bulley, who coached Nick as a teenager, said the fans love his former charge but his behaviour would change over time.

“Those little small moments in the match where Nick might get frustrated and say the wrong thing, it detracts from the performance, the amazing tennis that he’s putting out there,” he said.

“So, as he goes on and becomes a more mature tennis player, those things will go by the wayside and people will start to realise what a special talent he is.”

Nick now faces a tough third round game against Canadian Miles Raonic.

Christos said the dispute with the umpire would not hurt his chances.

“Nick’s now won two rounds in straight sets in the biggest tournament in tennis, and I haven’t read one story about the fact he’s blown away two top 50 players, all I’ve read about it that he’s had a little argument with an umpire,” he said.

-ABC