Jordan said the owners saw the buyer had done some charity work and sponsored children in need, which resonated well with them.
"It was just a feel-good decision for them," he said.
The sellers also liked the fact the buyer had a big family and thought the home would be perfect.
The property was first listed for sale in July 2016 through an expressions of interest campaign.
Paratz built the home in 1998. Records show they bought the property for A$750,000 a year earlier.
The six-bedroom, four-bathroom home is on a huge 4603 sqm riverfront block adjoining Lone Pine Sanctuary and includes a pool, tennis court and golf putting hole.
Features include floor-to-ceiling glass, a poolside pavilion, pontoon, theatre, library, games room and garage for six vehicles.
Jordan said the property attracted multiple offers because it was one of the few level, northeast facing blocks of land with direct river access that didn't flood in Brisbane.
"That was a very special piece of land," he said. "I think it was a good buy for that price."
Fig Tree Pocket has a median house price of A$1.2m, according to property analytics company CoreLogic.
The record sale price for the suburb is held by a mansion at 36 Needham Street, which last sold for A$9.5m in 2008.
The home is owned by Peter Bond, the founder of the collapsed Linc Energy, and is now back on the market after failing to sell at auction recently.
Jordan said interest in Fig Tree Pocket had grown in the past six to 12 months as people realised its value.
"It's this tranquil, serene setting that feels like you're miles away from the CBD when you're actually quite close, and it's value for money compared to some inner city suburbs."