Her brother Mike Cotton says he's longed to lay his sister to rest ever since and urged Dahlberg to come clean.
But the former Nelson city councillor told APNZ he could not expect Dahlberg to remain in jail for any longer.
"In terms of our justice system 20 years is quite a long time and if you kept him in prison another 10 years he still wouldn't tell us where her remains are.
"If he were to tell us, even indirectly, where Ann's remains were then we could move on with it. Just tell us where she's buried."
Dahlberg became eligible for parole in October 2001 and has appeared before the Parole Board 15 times since.
It wasn't until his 16th hearing, in December, that the board decided he no longer posed a threat to the community.
His release conditions include that he does not enter the Nelson region for the rest of his life and does not own a firearm.
Ms Urquhart and Dahlberg were married for three years - he was her third husband - but they separated in July 1991 after a domestic violence incident.
Mr Cotton said his sister remained in their rural house, about 8km north of Nelson, and the Family Court ordered Dahlberg to stay elsewhere.
"It was a strange thing, just prior to her being murdered ... both my father and I said to her 'you've got to be very, very careful, you really shouldn't be out there on your own'."
Shortly afterwards Dahlberg handed his three firearms in at the Nelson police station.
The prosecutor during his trial, Lowell Goddard, said he told officers Dahlberg wanted to leave the firearms with the police "in case something happened".
"Then here could be no question about where his firearms were."
A few days later he visited his son in Wellington and told him he wanted a rifle to go rabbit shooting and asked him if he could use his gun licence.
He bought a .22 Norinco rifle with a silencer and subsonic ammunition, which it is believed he used in the murder.
Mr Cotton suspected Dahlberg had killed his sister because he thought their marriage settlement was unfair.
"It's pretty obvious that he did it. I mean not just obvious, but by the court findings it's quite clear that he's guilty."
Ms Urquhart was a mother of three and worked in an accounting office.
"She was a pretty smart lady. The only thing she wasn't smart at was picking husbands," Mr Cotton said.
For reasons Mr Urquhart preferred not to discuss, the murder had torn the family apart.
"As a result of this half-witted Dahlberg killing Ann it's split our family really. We just keep out of each other ways now."
