Family man Roger Federer admits his unexpected run to the Australian Open semi- finals is starting to inconvenience at least one of his four kids.

The champion Swiss says he's loving his extended summer down under with wife Mirka and their two sets of identical twins, seven-year-olds Myla Rose and Charlene Riva, and two-year-olds Leo and Lenny.

The Federers have been in Australia since late December, with the 17-times grand slam winner choosing the Hopman Cup in Perth as the ideal place to make his comeback from six months out recovering from a knee injury.

But the 35-year-old concedes they weren't planning on his working holiday lasting this long.

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"With the late-night sessions I had to sleep in the morning so they knew dad can't be around that much in the mornings," Federer said after his straight-sets quarter-final win over Mischa Zverev on Tuesday night.

"But they enjoy Australia. Perth they had a blast and here as well.

"Melbourne they know better obviously because they have never been to Perth before.

"They have been active, they get outside every day, and they told me many times: 'Please don't lose, daddy, we want to stay here for longer'.

"For the first time today, one of my daughters said: 'It is actually okay. I'm happy to go skiing in Switzerland now'.

"So, I was like, come on. Give me one more match here. Maybe I can hang around for a couple more days. I think she's going to be all right with it."

Revealing a beautiful balance in his life, the tennis superstar said spending time in his down time was the best.

"I'm not going out as much here as I do usually in Switzerland," Federer said ahead of his all-Swiss semi-final blockbuster with great mate Stan Wawrinka on Thursday night.

"I like to take them (the children) in the outdoors, going out to nature or just being with them.

"With the boys now, it is hide and seek and all that stuff, you know, crawling around the floor, wrestling with them.

"And with the girls, it is - if I can help them with homework, or just talk to them, and just hear their thoughts, what's going on in their head.

"That's plenty for me right now in Australia."

- AAP