Sonny Bill Williams has a CV to match the best in rugby, but the code-hopping star has rarely been prouder than when he heard his sister had been called up to the New Zealand women's sevens team for the Olympic Games.

Williams counts two Rugby World Cups with the All Blacks and a Super Rugby title among his list of achievements in rugby union, while in league he was a two-time NRL premiership victor.

The 30-year-old has also held the New Zealand heavyweight boxing title and will look to add to his long list of accolades when representing New Zealand in sevens at the Rio Olympics.

But he is not the only member of the family gunning for gold in Brazil, with his younger sister Niall having been included in the women's squad, a huge cause of celebration for Williams and the rest of the family.

"I was happy when I got the phone call, but the biggest cheer we got in my household was when my sister made it," he told the Daily Telegraph in Australia.

"It's awesome, just seeing where she's come from, a mother of two, when she first started her journey she wasn't contracted, she had to get up in the early hours of the morning to do her training and then look after her girls and then train again at night.

"I'm proud of her, but at the same time there are a lot of media here and a lot of spotlight on myself and my sister, but for us it's not about us two.

"It's about this journey and this team we're in. We really want to go over there and compete well. Although it's pretty nice today, the hard work starts again tomorrow."