A four-year-old boy ate the contents of his nappy because he was starving, and slept in a buggy full of urine, his brother told a jury, with his mother on trial for the manslaughter of the little boy.
Hamzah's body was found in a travel cot in his mother's bedroom in September 2011. He had died 21 months earlier, in December 2009.
Qaiser Khan, 22, was giving evidence on the third day of the trial of his mother Amanda Hutton, who denies the manslaughter of her son Hamzah Khan.
Today, Khan told a jury at Bradford Crown Court how he went to the house between December 2008 and March 2009.
He said Hamzah slept upright in a urine-soaked buggy that "stank".
Khan said his brother was left in a dirty nappy and he witnessed him eating the contents.
"Hamzah appeared neglected," Mr Khan said.
He explained to the jury: "I was only at the house for a couple of days. The buggy smelled so bad of urine I got disinfectant and cleaned it out."
Khan was also asked about a text message sent from his phone to Hutton in December 2008.
Paul Greaney QC, prosecuting, said the text said: "Watch out Monday you bitch. I'm going to go to the police station to report you for child neglect and abuse. Look at Hamzah."
Khan said he did not remember sending it.
Asked by Stephen Meadowcroft QC, defending, if he was exaggerating what was happening at the house because he had a bad relationship with his mother, Khan said: "I've seen this with my own eyes."
Mr Khan told the court that when he was aged about 13, he was made to drink "mouldy, off milk" by his mother as punishment.
He said his mother would spend her days drinking. "She would go upstairs and drink and then I wouldn't see her for most of the day," he said.
Earlier, Khan refused to answer any questions when he first stepped into the witness box.
But after a break he returned to court to give his evidence.
The prosecution has told the court Hutton starved her son to death.
The defendant told police her son died after he was taken ill.
Meadowcroft said he was suggesting that Hutton was coping before Hamzah's death.
The barrister said: "The child died tragically and it wasn't her fault. After that, she collapsed."
Khan said: "Urined buggy - was that coping? That was before 2009.
"It was quite clear she wasn't coping. She hadn't cleaned the house up and she didn't clean the nappies."
Earlier, the court heard how Hamzah's father, Aftab Khan, urged police to go and check Hamzah and told officers he was going to report his wife to social services.
The jury of eight men and four women were read a police interview with Aftab Khan conducted in 2008 when he had been arrested for hitting Hutton.
Judge Roger Thomas QC warned the jury to bear in mind the interview took place as Aftab Khan was under suspicion of an assault - an offence to which he later pleaded guilty in court.
In the interview Aftab Khan claimed Hamzah was undernourished and neglected.
He said: "Believe me, I'm going to get in touch with them (social services) because it's gone so far now."
Khan told the officers he wanted to take Hamzah to a doctor but Hutton wouldn't let him.
He said: "I've told her time and time again there's something wrong with that child - take him to the doctor."
Khan described how he changed Hamzah's nappy after Hutton had left it for a day and a half.
He said his wife's problems were due to her alcohol consumption.
But when Detective inspector Ian Lawrie, of West Yorkshire Police, was asked if Aftab Khan did report his concerns to social services, the officers told the jury: "There's no record I'm aware of of any such referral."
Lawrie said police did go to the house following the interview with Aftab Khan.
He also confirmed police had been called to the house on eight separate occasions in the two and a half years up to 2008.