NRL and All Blacks great Sonny Bill Williams has bid his children a very emotional farewell at Sydney airport – as mystery surrounds his reason for leaving them for the next eight weeks.

The footy star turned boxer, 39, shared a touching post to Instagram on Monday explaining how difficult it was for him to be away from his family.

‘The older I get, the harder it is to leave the lovins. See you in 8 weeks my loves,’ he posted.

Alongside the caption he shared photos and video of himself embracing each of his five children – Zaid, Essa, Iman, Aisha, and Mohammed.

It is rumoured that Williams is heading into fight camp, having recently agreed to a long-awaited mega-fight with fellow NRL great Paul Gallen.

After more than a decade of trash talking and stalled negotiations, the former footballers are now set to meet in the ring on July 16.

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Sonny Bill Williams has bid his children an emotional farewell at Sydney Airport

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The cross-code superstar is rumoured to be heading into fight camp for his clash with fellow NRL great Paul Gallen

They’ll clash over an eight-round main event contest, with each round lasting two minutes.

The fight, which will be shown live on Stan, will see the fighters bank $1million each as part of a 50-50 split.

Daily Mail Australia spoke to Williams on Monday before he flew out, but he would not comment on where he is at with his fight preparation.

If he is flying to his pre-bout camp, it goes to show Williams is taking the heavyweight clash very seriously.

SBW, who keeps himself in tremendous shape, is adamant he will be getting his hand raised at the end of the clash.

‘I win because I’m a better boxer,’ Williams told the Sydney Morning Herald last month.

‘I win because the only way he can beat me is to knock me out, and I don’t think he has the power. That’s the honest truth.

‘I’m a better boxer, a better athlete.

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Williams revealed that he will be away from his family for the next eight weeks – but the reason for his absence remains a mystery

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The NRL premiership winner has signed on to fight Paul Gallen on July 16 after more than a decade of trash talk between the pair

‘But the one thing he brings to the table – and I’ve always said this, I respect Paul for what he has done in the ring – he’s a brawler and he’ll come [at me].

‘I still want bragging rights, I still want to give him a good hiding. He talks too much, I’m going to smash his face.’

Last month, cruiserweight champion Jai Opetaia branded the bout as ‘soft’.

‘It’s not an attack, I’m taking the p**s – but two-minute rounds is soft, bro,’ Australia’s best boxer told News Corp.

‘You want to put on a big-time main event, well, boxing is three-minute rounds.’

And Gallen believes Opetaia was right.

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It is unknown where SBW will be training for the blockbuster bout

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Each fighter is set to pocket $1million for the heavyweight showdown

‘I woke up this morning to the king of the cruiserweight division, Jai Opetaia, calling mine and Sonny Bill Williams’ fight ‘soft’ – well he’s one hundred per cent correct,’ Gallen said.

‘Sonny, you’re happy to tell everybody you’re a better athlete than me, that you’re a better boxer and you’re gonna give me a hiding.

‘Well, mate, let’s do it properly. Boxing is fought over three-minute rounds.’

Williams last fought in 2022, suffering a shock knockout loss to MMA star Mark Hunt. Despite the setback, his athletic pedigree and star power make him a huge draw.

Gallen retired from the sport in 2022 after a win over Justin Hodges, but has always said he’d like to take on Williams.

The only two blemishes on Gallen’s pro record were in Australian heavyweight title bouts against Justis Huni and Kris Terzievski.