Rowan Baxter killed Hannah Clarke, Aaliyah, 6, Laianah, 4, and Trey, 3, when he doused them in petrol and set their car alight in a Brisbane street on Wednesday morning.

He died shortly after stabbing himself in the abdomen with a knife.

The shocking attack has seen more people turn to domestic violence services for help, Prevention of Domestic and Family Violence Minister Di Farmer says.

"I've spoken with many people who work in the DFV sector and everyone has been absolutely devastated by the deaths of Hannah and her little babies," Ms Farmer told AAP.

"But they've also said that in the past few days, they've seen an incredible surge in calls from people asking for help - and importantly, from people asking for help to stop being violent."

Details of the couple's toxic split continue to emerge with revelations Rowan Baxter had been in counselling and had rejected a shared custody offer.

The offer would see him with the children several times a week, according to the ABC.

Baxter rejected his lawyer's advice during a mediation session with Clarke and refused to sign the order that would allow him 165 days of custody per year.

Instead, Baxter signed a non-legally binding agreement that gave him just as much access to the children their mother.

Ms Clarke's mother Suzanne told Channel 9's A Current Affair that her daughter first experienced psychological trauma and abuse from her estranged husband, which slowly turned physical, leaving Ms Clarke in fear for her life.

Mrs Clarke was blunt in her assessment of Baxter: "He was evil."

Mrs Clarke said her daughter was "scared to leave" but had been making small steps to move away in recent times.

She said her daughter only last week brought up the idea of organising a will.

The family claims Baxter stalked Ms Clarke through her mobile phone and knew where she was at all times.

"She wasn't allowed to wear bikinis, she works in the fitness industry and wasn't allowed to wear shorts. She had to cover up," Mrs Clarke said.

"In the beginning we thought he was a prude, but in hindsight we know there was more to it than that. He was controlling. It was Rowan's way or the highway.

"He could manipulate her. The night before he killed them he was on the phone to the children crying and she hung up or the children hung up she said to me 'Mum I feel so bad for him'.

"He was very good at playing the victim. We knew there was no way she could just say, 'I'm going and walk out the door'.

"She said, 'What happens to my babies if he kills me?'"

The Clarke family say more needs to be done to ensure victims are better protected from their abusers, and are hoping to establish a support system for women suffering at the hands of domestic violence.

On Saturday, they posted a thank you message for public support as donations for the family soared past $206,000.

"It is the most beautiful thing to see so many people offering donations and such kind messages - It has given the family hope for change and touched their hearts to know so many care," said Hannah's sister-in-law Stacey Roberts.

She said the family had been pushed into debt by Baxter's "inability to support his family financially for years and to fight this monster".

Australian Associated Press