The family has chosen to remain anonymous and told lottery staff they had not been planning to buy a ticket, but had been forced to visit the Boulevard Newsagency when they discovered they had run out of cereal and decided to buy a ticket while they were there.
They watched the draw at home and marked off the numbers as they were pulled from the machine.
"The numbers started getting crowded on my ticket while I was circling them and I thought, 'this is looking good'," one of them said.
The family has already racked up a few previous division 2 wins and always believed it was only a matter of time before they hit the big one.
"I'm a committed Lotto player and I was determined to win, we are very happy," one of them said and the serial winners admitted they plan to continue playing, and are hoping for a further big win.