Mark Lundy's sister wants him freed from prison to live with her as he prepares for a second murder trial.
Caryl Jones said last night that she hoped her brother would be bailed to her Taupo home.
She had kept the ruling secret for 24 hours after receiving a phone call from Lundy on Sunday night.
"We're absolutely over the moon. The Privy Council was obviously listening to what was being told to them. It was a big 'wahoo' moment," she said of learning the news.
Mrs Jones said the next step was getting her brother released. "We'll get the application lodged as soon as possible and hopefully he'll be bailed to my house."
Her other brother Craig Lundy does not share her belief in Mark's innocence but was unable to be reached for comment.
Glenn Weggery - who discovered the bodies of his sister Christine and niece Amber - could also not be reached for comment but is staunch in his belief that the right man is behind bars.
Christine Lockett, a close friend of Mrs Lundy, told TVNZ that the news was devastating for family and friends who now had to "relive their heartache".
Geoff Levick, who researched the case for years and was responsible for organising the Privy Council appeal, said it had been a long, hard struggle.
"I made Mark Lundy a commitment three or four years ago when I said to him that I will get him to the Privy Council.
"From that perspective, I was happy months ago because we got there. This is the icing on the cake."
Assistant Commissioner Grant Nicholls said the police would discuss the ruling with Crown Law to determine the next steps. "This is likely to include evaluation of what evidence needs to be prepared and the availability of witnesses."