"Every day I suffer. Every day of my life.
"I close my eyes and that boy is always in my mind," Ms Rimene said.
"For 26 years justice was never served, and I'm the one that has to deal with it."
Ms Rimene said she had lost custody of Gavin when he was four-and-a-half years old after her brother was shot dead by the Mongrel Mob.
"My brother was very close to me so his death shattered my whole life."
Family members "and the court" told Ms Rimene she was unfit to be a mother and Gavin went into foster care with Peneha.
"She always said to me, 'you go away and get yourself on track and you can have your kid back'," Ms Rimene said.
"I went to [Gavin's] funeral and blocked it out for 26 years."
Ms Rimene now has four daughters between the ages of 10 and 26 who "decided that they wanted their brother acknowledged in the March for Moko".
The Justice for Moko March will be held in central Masterton on June 27, the same day as the sentencing of Moko Rangitoheriri's killers, Tania Shailer and David William Haerewa.
The series of nationwide marches was sparked by the violence which killed the 3-year-old, who was savagely beaten over several weeks by his carers.
The Masterton march is being organised by Liz Rikiti and Amanda Dette.
"I want people to come to this march because there is a very real and very local aspect to it," Ms Rimene said.
"I want to march, I want to share with people that justice wasn't served for my kid.
"Now my boy can lay at rest and be at peace because I'm bringing him justice, not through the courts, but through joining this march.
"It's for him, and all of those kids that have been hurt."
Ms Rimene has spoken with St Patrick's School, which Gavin briefly attended, Solway College and Lakeview School, to rally support for the march.
Her niece in Wellington has designed shirts in remembrance of Gavin for the march.
