Pat Rafter gives his fans a rare glimpse into the surprising mission he's on in retirement - and lifts the lid on a family tragedy

Aussie tennis great Pat Rafter has offered an insight into the passion that's driving him more than 20 years after he retired  - and also revealed his thoughts on a previous family tragedy that saw a relative jailed.

A two-time US Open Grand Slam winner, the 51-year-old resides in the Byron Bay hinterland - and after previously owning a waterfront property just down the road, he couldn't be happier.

The father of two has been busy - his family has laid an estimated 7500 native plants and trees on their 26-hectare property - and also planted 10,000 eucalyptus trees in a bid to create a koala corridor and sanctuary.

'I really love working the land, and it occupies a lot of my time,' he told News Corp.

'It's very important to us to regenerate the property back to what it once was, and we are doing it in segments.'  

Seeing echidnas, bandicoots and swamp wallabies has become the norm, with Rafter and his wife Lara relishing the quiet life.

Their children - Joshua, 21, and India, 18 - have moved out as they look to launch their own careers and lives.

The former sporting heart-throb, who reached the world number one ranking in 1999, also discovered his family has a criminal past.

The Rafter's appeared on the SBS show Who Do You Think You Are? with a historian revealing the tennis star's great-grandfather on his father's side was often in trouble with the law.

David Dee's family came out to Australia from Ireland and settled in Townsville in 1875 as free immigrants - and the baker had a short fuse.

Dee was once charged by police with using profanity, with the offending words 'bloody bugger and damn rascal.'

Court appearances and physical altercations followed, before Dee was jailed for four years after fighting another man.

His wife Teresa was left to raise five children - and after she found love elsewhere with her husband behind bars, Dee sadly died broke, estranged from his children and alone in Cairns back in 1918.

Rafter acknowledged Dee 'made some really poor choices' - but he was still fascinated to hear about his early family history.

He also confirmed he doesn't play tennis much these days - but did compete at the recent Senior World Padel Championships in Spain - in the 50-54 men's division.