Mitch and Mark's heartwarming plan for their Block winnings

The Block auctions are always nerve-wracking but Mitch and Mark had the added pressure of being first up. But the bids quickly rolled in and the couple was ecstatic that they made a profit straight away.

"We made $10,000 at the first bid, and that for us was like we've already won," Mitch told 9Entertainment after the auction.

Mark added, "The opening bid was already over the reserve [set at $2.99 million], it was $3 million and I was like, 'Oh my God, it's already over reserve'."

Mitch and Mark's house sold for $3.374 million, which earned them a total of $384,000 in profit.

"It just kept going up and up and up, we lost track of where it was actually. Once it got past 300 I thought this is just such an incredible gift, but we could not be more excited and more appreciative."

When it comes to spending their winnings, the Bondi granddads will be living up to their nickname by using some of the cash to help their granddaughter Carli.

"We've got a very sick granddaughter and we can help with that and that's very important to us," Mitch said.

Mitch and Mark opened up to A Current Affair about Carli's battle with Dravet syndrome, a form of epilepsy. They hope part of their winnings can assist with Carli's treatment.

And as for the rest of the cash, Mitch and Mark plan to pay off their own properties.

"We are in debt up to our eyeballs with mortgages so that'll help," Mitch said.