A sibling of a four-year-old boy allegedly murdered by his mother and stepfather told a court they saw him being held underwater in a bath at the family home.
Daniel Pelka died from a head injury in March 2012 in Coventry after an alleged campaign of "incomprehensible" cruelty.
His mother Magdelena Luczak, 27, and her partner, Mariusz Krezolek, 33, both from Poland, deny murder.
The child said they tried to protect their brother from the pair.
Jurors at Birmingham Crown Court saw recorded evidence of a police interview with the sibling, who cannot be identified.
The child witness was filmed sitting in a room filled with cushions and playing with toys while a police officer asked questions.
Ms Luczak and Mr Krezolek are alleged to have starved and murdered the primary school pupil, who was confirmed dead in the early hours of 3 March after paramedics were called to his home.
His sibling described how they would often ask for extra food so that they could give some to Daniel, who they said was not allowed downstairs.
The child said Daniel was not allowed to leave his bedroom to use the toilet and had been expected to defecate in his bed.
'Didn't do anything'
Speaking about the occasion when Daniel had been in the "really, really cold" bath, the child said: "[Mr Krezolek] bashed Daniel's head against the bath. He pushed him."
The child showed that Daniel had suffered a head injury and was asked whether Daniel was taken to hospital.
"No, I looked after him.
"[Ms Luczak] was holding him underwater. [Mr Krezolek] told me not to tell anybody. Daniel cried. They didn't do anything."
The child witness said they often saw Mr Krezolek drunk and said he "smashed [Ms Luczak] loads of times - 11 or 10 times".
They added: "He done some really naughty things."
The witness continued: "Sometimes he done it to [Ms Luczak] and she telled him to stop it and I can't because he... When he's hurt [Ms Luczak] I can't be brave because I am really sad and I think [Ms Luczak] started to be rude to my brother."
Daniel's sibling described one occasion when he could not be woken up.
They said: "I tried to wake him up but I didn't, I couldn't. I listened to his heart but it didn't, I couldn't, hear his heart. It couldn't beat.
"I shouted to [Ms Luczak] and [Mr Krezolek] and [Ms Luczak] shouted, 'what's the matter?' but they didn't come to see."
The child also said they would cook dinner for Daniel.
They said: "I had my money I got from the bank. I found a card on the floor. I used to go to a shop with my brother and used to buy things for him that [Ms Luczak] couldn't see."
Daniel's sibling was asked if they helped their brother with food.
"Yes, everything," they replied.
Mr Krezolek and Ms Luczak have admitted child cruelty, but deny murder and causing or allowing Daniel's death.
The witness was later cross-examined by defence barristers on a live videolink, via an intermediary in the same room as them.
They also claimed to have hidden food, including toast, to give to Daniel.
"We had to look after ourselves," the witness told the court.
"I had to make food for him, I had to clean him up."
During cross-examination, the child told Stephen Linehan QC, representing Ms Luczak, that Mr Krezolek had hit Daniel, who had been put in a bath of cold water on two occasions.
The trial was adjourned until Thursday.