The dispute ended up in court, with Justice Kit Toogood ordering that an auction be held to settle the matter.
If the property failed to sell, he said, it should go to the younger couple, who would pay the parents half of its value.
About 25 people attended the auction yesterday, where the bidding began at $2m.
It failed to attract a single bid.
The younger Gregorys, who live at the address, wore baseball caps and sunglasses as media waited outside. They declined to comment on the outcome.
The senior Gregorys, who own a home next door, were not present and could not be reached for comment.
Trevor Gregory has previously said that despite the court battle he was hopeful he could eventually mend the relationship with his son.
"People will draw their own conclusions about this but we needed to go to auction because there are more people involved than just me."
The property, which was marketed by Barfoot and Thompson, was described as a grand home with views across the harbour to the Waitakere Ranges, Te Atatu Peninsula and West Harbour.