Patricia O'Connor's son has said that when he and his father decided to go to gardai days after she went missing, his sister Louise "didn't want us to report it".
Richard O'Connor also told a Central Criminal Court jury his sister "wore the trousers" in her relationship with murder accused Kieran Greene, who was "something of a fool and a moron".
Mr O'Connor was giving evidence for the prosecution in the joint trial of four people who are charged over the grandmother's death in 2017.
Kieran Greene (34), then-partner of Louise O'Connor, is charged with murder.
Louise (41), her ex -partner Keith Johnston (43) and their daughter Stephanie O'Connor (22) are accused of impeding the investigation.
They all deny the charges.
Patricia O'Connor (61) was allegedly murdered on May 29, 2017, at the house at Mountain View Park, Rathfarnham she shared with family, including Louise, Stephanie and Mr Greene.
Her remains were found scattered in the Dublin and Wicklow mountains between June 10 and 14 that year.
Richard O'Connor, who had not lived at the family home for years, said "there was a fair bit of friction", in the house that "stemmed from Louise and her family living in the home and not keeping the usual upkeep of the house".
His mother had retired from her hospital cleaning job and "was at home more often".
"There wasn't enough being done for the amount of them in the house," he said. "It put a strain on her constantly."
"I saw my mam giving out, saying 'move your lazy arses', or tidying up after the kids. Most of that was directed at Louise."
May 30 was his birthday and when he had no contact from his mother, he contacted Louise on May 31.
"That is when she informed me that my mam had left with a suitcase and run off somewhere after an argument," Mr O'Connor said.
He was asked to describe his mother.
"She was a straight shooter and if you were in the wrong, she would tell you you were in the wrong," he said.
He was "worried" when his mother was missing and had "no idea" where she might have been.
On June 1, he went to the house, and Louise, their father and Kieran Greene were there.
Prosecuting counsel Roisin Lacey SC asked if an agreement was reached that Patricia should be reported missing.
"I agreed with my father, Louise didn't want us to report it," he replied. Kieran Greene "didn't say a thing", he said.
On June 11, he said he walked to the shops with Mr Greene and asked about his mother being missing.
"There wasn't a budge out of him," he said.
He agreed with Mr Greene's barrister Conor Devally SC he had told gardai Mr Greene was "something of a fool and a moron".
He agreed Louise was "sharper" than Mr Greene, saying "she would be cute enough, yeah."
"Louise wore the trousers, yeah," he agreed.
Mr O'Connor had described his mother as "a bit of a doer, who would get stuck in", and "hated laziness".
Cross-examined by Louise O'Connor's barrister Michael Bowman SC, he said Louise had told him "there's no need to involve the guards. I said: 'I don't care, I'm going down, even if I have to go myself'."
It struck him as unusual, he said, and "my mam wouldn't just run off for no reason."
He agreed he did not mention this in his garda statement.
The trial continues.