Tuitania Barclay's upbringing meant she would never have walked out on her three children, her sister says.
Like many of her siblings, Tuitania - the youngest of 15 children - was placed for adoption at her birth, on May 10, 1974, her sister Chanel Kerr said.
As a teenager she later met her birth mother in Australia, a reunion which did not end well.
''She and her partner got kicked out,'' with the failed reunion costing the young teen thousands of dollars.
The sisters became close after meeting as teenagers in Dunedin, Ms Kerr said.
Ms Barclay, who attended Kavanagh College, was placed in foster care after her adoptive mother died.
Detective Constable Matt Preece said foster care ''did not go well for her'', adding Ms Barclay in her teens was ''in with a bad crowd''.
Then followed a period of drugs and prostitution, but a stint in prison provided a chance to cut ties with her former partner, he said.
''I think she realised that he was not a good influence on her.''
Ms Barclay - also known as Tui and later Tania - had to demonstrate to authorities she was responsible enough to look after her son.
''She made a big effort.''
Tuitania, who was Caucasian with a small build and about 157cm tall with dyed dark brown hair, had also gone by the names of Tuitania McIntosh, Tuitania Brown and Sandra Williams.
Once out of prison, she worked at the Rugby Hotel, noting in her diary ''it wasn't worth it, wasn't making money any more''.
Ms Kerr said both sisters wanted the best for her children, promising ''we would love our kids and be there for them''.
''I just can't see her walking away from them ... It doesn't matter what she would have done, she would have taken them.''
Ms Barclay would have hated being described as a former prostitute, and had worked hard to put that life behind her.
''There may have been some problems with [former fiance Bill Brown]. I don't think it was as rosy as what people make it out to be. He didn't know anything about her past until she disappeared and then it all came out of the woodwork,'' Ms Kerr said.
Detective Senior Sergeant Malcolm Inglis said Ms Barclay appeared to be a caring mother who wanted to turn her life around.
Police were motivated to solve the cold case and provide closure for the family members, who were aware it was being treated as a homicide.
''We are trying to dig as deep as we can.''
Timeline
May 10, 1974: Tuitania is born in Dunedin. The youngest of 15 siblings, she is put up for adoption, and takes the name of her new family.
During her teen years: She attends Kavanagh College and is later taken into state care when her adoptive mother dies.
July 10, 1995: Her first child, a boy, is born.1997: Spends several months in prison. Vows to turn her life around so she can be with her son.1999: Starts a relationship with Bill Brown, who is 10 years older.
Dec 27, 2000: Her second son, and first with Brown, is born.
April 2001: The couple move to a Wakari Rd address.
May 2001: The couple become engaged.
April 28, 2002: Her third son, and second with Brown, is born.
Aug 20, 2002: Plunket check at her home.
Aug 24, 2002: Her Mitsubishi Mirage is ticketed for not being registered or warranted while parked in Princes St.
Sept 2002: Winz is notified of a change in the couple's relationship.
Sept 4, 2002: Her benefit is cancelled.
Sept 17, 2002: Last confirmed sighting of Tuitania at her Wakari home.
Sept 26, 2002: She writes on a date-stamped envelope ''Here the ring back who wants to Marry a mental Bitch''.
Oct 10, 2002: Plunket makes a home visit. It is noted she is not home.
Oct 15, 2002: Her eftpos card is used, with a couple of hundred dollars withdrawn.
Jan 2003: Bill Brown is urged to report her missing.
Feb 28, 2003: Bill Brown reports her missing. A missing person file is opened.
April 2003: Police increasingly concerned she has had no contact with her infant son, who has had his first birthday. Police also confirm she has not opened a bank account under any of her aliases.
May 17, 2014: Police hold a press conference to confirm they are reopening a cold case.
Yesterday: Police offer a $50,000 reward for information to solve the mystery of her disappearance.
