The 10-year-old said his father Gurpreet Singh, who is accused of murder, had turned Sarbjit Kaur over and “tried to wake her up”.
He told police in a video interview her eyes were closed and her mouth shut, and she showed no signs of breathing, a jury at Birmingham Crown Court heard.
The court heard his sister, aged 11, was the first to enter the house in Rookery Lane, Penn, Wolverhampton, and see signs of upheaval.
She called to her father who, after unlocking the front door, had returned to the car to fetch something from the boot.
The wealthy businessman, aged 43, ordered the children to get back into the car but while he was on the house phone to the police telling them he had been burgled, “for some reason” he beckoned them back into the house, the boy said.
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The young boy had followed his father to the sewing workshop where Sarbjit’s body was found.
His father had thrown the phone down and tried to wake her.
At that point his 11-year-old sister appeared and had picked up the receiver and continued the conversation with the 999 operator, the court was told.
Her father told her to ask for an ambulance quickly, the jury heard. She said her little brother was “shaking”.
The children had been picked up from school that day by their father, which was unusual, the jury was told.
In separate interviews both told detectives that it was normal practice to be driven home by their 38-year-old stepmother Sarbjit, the defendant’s second wife who they referred to as their mother.
The boy said his father occasionally picked them up in the afternoon but usually only if their mother was ill.
Both children recalled that the defendant had “promised” to do so when he dropped them off at school that morning.
Singh is alleged to have strangled his wife with the help of an accomplice between 8.15am and 9am on February 16 last year after dropping the children at school and before leaving for work.
He is also accused of soliciting the murder of his first wife, Amandeep Kaur, the children’s mother, in 2013.
She died in India of a brain haemorrhage the following year.
Singh, of Coalway Avenue, Penn, denies murdering Sarbjit Kaur and soliciting the murder of Amandeep Kaur.
The trial continues.