On June 23, Mr Mohamad Nasser Abdul Gani sat in court and listened to the horrific abuse his son was subjected to before he died.

He was heartbroken.

"I imagined how they kicked my son, punched, forced him to eat chilli," said the 42-year-old former cleaning supervisor, who had sleepless nights after the court hearing.

"I kept having images of my son being bullied," he said, tearing up when he talked about the boy.

Mr Nasser, the biological father of Mohamad Daniel Mohamad Nasser, had never seen his two-year-old son alive.

The boy had been kicked and slapped almost daily by his mother Zaidah, 41, and her boyfriend Zaini Jamari, 46, in a five-week campaign of torture that ended in his death.

Mr Nasser said his former wife appeared defiant and unremorseful when she was convicted around two weeks ago.

Yesterday, she showed no emotion in court as well. She was sentenced to 11 years' jail and Zaini, 10 years and 12 strokes of the cane.

"It is not enough, we will never forgive them for what they did," said Mr Nasser, who broke down outside the courtroom.

"I keep thinking about my son. I hoped that I could celebrate Hari Raya with him. But I can't," he said.

He had married Zaidah in Batam in early 2012, but saw her with another man - Zaini - a few months later. Not knowing that she was pregnant with Daniel, he divorced her that same year.

He got involved in drugs after their separation, and Zaidah told him about their son just before he was sentenced to 18 months' jail.

He said: "She told me I would never get to meet the baby."

And he never did.

Behind bars, Mr Nasser signed a document acknowledging that he was Daniel's father. He resolved to turn over a new leaf and care for the boy upon his release.

But despite searching for a year, asking friends for Daniel's whereabouts and waiting at the block where Zaidah used to live, he could not find mother and son.

The first time he saw Daniel was when he identified his son in the mortuary on Nov 27 last year.

The first time he took Daniel in his arms was when he and his relatives buried the child on Nov 30.

Said his brother, Mr Abdu Manaf Al Ansari, 48: "When (Mr Nasser) stepped out of jail in 2014, he promised me, 'I'm going to change'. He had never hugged me so tightly before."

Mr Nasser has stayed out of trouble since, said the religious teacher, who is the oldest of five siblings.

"If (Zaidah) could not take care of her son, she could have given him to Madam Masita," added Mr Manaf.

Madam Masita Hussin, a housewife, had taken in Daniel as a month-old baby through a friend and raised him as her own.

Mr Manaf said his family could also have cared for the boy. "We could have given him a good life, a good education."