Later, he stabbed the boy with a two-pronged knife, repeatedly bashed his head against a wall and used a large piece of sandstone to bludgeon his skull.
"One could expect a mother could rely on her adult son to provide protection from harm," NSW Supreme Court Justice Stephen Campbell said before sentencing Rhodes to a maximum 40 years behind bars.
"(The child) would have known the offender was intending to kill him and like Linda he would have been terrified in his final moments of life."
Rhodes hung his head throughout the judgment and did not appear to show any emotion as he was led away after the sentence.
The court heard he had come home on the night of the attack and told his 19-year-old niece, "we're going to have some fun tonight", to which she replied, "whatever".
After starting to attack his mother, Rhodes said "they're in the house" and "don't worry, I'll get rid of them".
He later told the now-dead boy and another child that had tried to hide: "If you move, talk or speak, I'm going to stab you with this knife."
"Die, just f***ing die. I don't care," the court heard he said after killing the little boy.
Rhodes, who pleaded guilty to the murders in a local court, told police he couldn't remember anything and was "insane".
Justice Campbell said he was sceptical about Rhodes' amnesia claims but did find he was suffering from a drug-induced psychosis, after consuming ice and cannabis on the day of the killings.
The child's body was found near a tree on the property, while Ms Adams' was found face up about two metres from the door of her neighbours' home.
She had tried to seek refuge in the house, Justice Campbell said.
After the murders, a bloodied Rhodes ran at a member of the public and then tried to get in her locked car as she beeped her horn for help.
He also wrestled with the first police officer on the scene, whose Taser had twice misfired. Rhodes will be eligible for parole in September 2045.
"No matter how long the sentence is, it will not bring back two beautiful people we have lost," Ms Adams' daughter Tina Rhodes said after the sentence.
