There were highs and lows as they fought to raise coercive control awareness in the aftermath of the shocking incident.
However, their long ride appears almost over thanks to a landmark bill in Queensland's parliament on Wednesday.
Coercive control is set to become a standalone offence, with Queensland to join NSW by criminalising it under proposed laws introduced by Health Minister Shannon Fentiman.
The new offence will carry a maximum penalty of 14 years' jail.
The Clarkes welcomed the bill outside parliament on Wednesday along with the family of Allison Baden-Clay, who was murdered by her husband 11 years ago.
"We've had some tears and I'm starting to go now, but it's been a collective effort," Sue Clarke said.
"Over the years it's been one hell of a rollercoaster ride - highs and lows - but we're getting there," Lloyd Clarke said.
Hannah, 33, and her young children - Aaliyah, Laianah and Trey - died after being set on fire in their car by her estranged husband Rowan Baxter in February 2020.
Sue and Lloyd Clarke have been advocating for coercive control to be criminalised ever since, earning 2022 Queensland Australian of the Year honours.
They operate the Small Steps 4 Hannah Foundation, which educates children and supports victims and their families.
Coercive control is a form of abuse where perpetrators display a pattern of manipulative behaviour designed to intimidate and isolate the victim.
"It's very subtle. When (Hannah) first started going out with him, he got her to shut her Facebook page down ... she couldn't walk up the beach in bikinis and slowly over time, more and more things come," Ms Clarke said.
The Clarkes had been joined by Ms Baden-Clay's family in the fight for coercive control criminalisation.
"I believe that Alison didn't realise what she was going through," Ms Baden-Clay's sister Vanessa Fowler said.
"We didn't see any black eyes or broken bones. All of that was insidious, and it was happening behind closed doors."
The families of Hannah Clarke and Allison Baden-Clay advocated for the reforms.
The Queensland premier saluted the Clarkes for their dedication, saying they deserved credit for the new laws.
"Anyone who has met them has been touched by not only the tragedy that they have gone through but how they have now devoted their life to making a difference," Annastacia Palaszczuk told parliament on Wednesday.Â
Queensland passed laws in February to define domestic violence as including behaviour patterns over time.
Ms Palaszczuk said coercive control had "no place in modern Queensland".
The new law is expected to come into effect in January 2025.
Ms Fentiman said communities could now focus on educating women and families to identify when coercive control was occurring and reporting it.
Sue Clarke (centre), mother of Hannah Clarke, hugs Priscilla Dickie, mother of Allison Baden-Clay.
The government will also address an affirmative model of consent in the bill.
It will criminalise the tampering or removing of a condom without consent - called stealthing - to bring Queensland in line with other jurisdictions, barring the Northern Territory and Western Australia.
In addition, Queensland courts will also consider relevant domestic violence or criminal history in their decisions.
They will have more power to respond to protection application orders to protect people most at risk, and award costs to prevent perpetrators from using the legal process to abuse victims further.
Domestic violence complainants and other witnesses will be under the protected witness scheme, and courts will be allowed to give directions to juries and hear expert witnesses on DV.
1800 RESPECT (1800 737 732)
Lifeline 13 11 14
National Sexual Abuse and Redress Support Service 1800 211 028
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