How do you bury two sons? Kathy Kelly will never stop fighting for Thomas and Stuart.

It was a cold Saturday night in July 2012, when Ralph and Kathy Kelly received a phone call.

Thomas, their eldest son, had left home just after 6pm to attend a friend’s 18th birthday. He was more excited than usual, because it was that night he was planning on asking the girl he liked to be his girlfriend. He had never done that before, and had spent hours talking it through with friends.

They were meant to meet under the iconic Coke Sign in Kings Cross, but Thomas didn’t know the area particularly well, so got out of the taxi on Victoria Street about 200 metres away.

As Thomas and the girl he liked walked hand in hand towards the main street, an 18-year-old named Kieran Loveridge who had already been involved in altercations all over the city that night, spotted him.

LISTEN: Mia Freedman speaks to Kathy Kelly about the grief of her children on No Filter. Post continues below. 

Kieran didn’t know Thomas. He didn’t know Thomas had a younger brother, Stuart, and a younger sister, Madeleine. He didn’t know how much Thomas loved playing the drums and the guitar, or how much he treasured his four pets.

He didn’t know that Thomas just wanted to kiss the girl he was holding hands with, or that he was full of dreams and ambitions.

Keiran didn’t know that when – for no reason at all – he punched Thomas in the face.

And that would be the last thing Thomas ever saw.

When the phone rang that night, it was St Vincent’s Hospital telling Ralph and Kathy that they needed to get to the hospital as quickly as possible.

"I think I knew the moment I saw him that he was already gone," Kathy tells Mia Freedman on the latest episode of No Filter.

She doesn't recall how she reacted. There were lots of words and numbers and phone calls to grandparents and aunties.

The family were by Thomas' bedside two days later when they watched his 18-year-old heart, stop.

"The only comfort I have," Kathy says, "is that he didn't see anything coming... he was happy. He was contemplating how he was going to kiss this girl."

CCTV captured the perpetrator, and what followed was a torturous trial that played out in the public eye. Calmly, Kathy says, "the offender said the punch didn't kill Thomas, the pavement did."

The Kelly family watched countless character witnesses support Keiran, and at no point did they receive an apology from Keiran himself or the Loveridge family.

Keiran was first sentenced to five years and two months for his attack on Thomas. But in July 2014, the NSW Court of Criminal Appear re-sentenced him to a minimum of 10 years, two months jail, partly because of an increase in the minimum sentence for manslaughter from four years to seven.

Stuart Kelly, then 16, said outside the courthouse,  "I no longer have a brother, instead I have a hole in my life, and that's something I'm meant to accept... I can tell you firsthand that to experience this kind of pain at such a young age is just … it's just too hard."

But their sense of overwhelming injustice which began as anger, slowly turned into determination.

“How can you sit back and see your child has lost 70 to 80 years of his life and not fight for that? That’s where it starts”.

Ralph and Kathy began the Thomas Kelly Youth Foundation, with the Take Kare initiative, mirroring Thomas' initials. Take Kare is all about responsible drinking, and looking out for friends, family and strangers.

But Thomas' death also led to policy change. The one-punch attack highlighted the epidemic of alcohol-fuelled violence, and was the catalyst for the introduction of lockout laws in NSW.

The Sydney lockout laws, introduced in early 2014, required all nightclubs, bars and pubs in the CBD precinct to enforce a lockout at 1:30am (no new patrons to enter premises) and last drinks to be called at 3am. The legislation was highly controversial, with The Keep Sydney Open campaign leading to enormous demonstrations. Businesses argued that the laws were crippling them, and many said it was destroying Sydney's nightlife.

The laws became (unfairly so) synonymous with the Kellys. Thomas' memorial in Kings Cross was vandalised, and had to be rebuilt - more than once - by locals.

This was the Kellys' punishment for trying to make the streets of Sydney safer, so no young person would suffer the same fate as their son.

Kathy says, “Since the lockout laws have come into play since February 2014 - there hasn’t been a single serious brain injury death at St Vincent’s hospital. And when Thomas was killed in July 2012, there were neurosurgeons on standby every single weekend… and facial reconstruction surgeons there every Monday putting people back together”.

The Kellys were subject to scathing online harassment, and Stuart in particular was the victim of vicious and unrelenting bullying.

At 18, Stuart began college at University, but less than 24 hours later Kathy says, "he came out of there a broken human being."

For months, Stuart hardly left his bedroom, until in July 2016, the 18-year-old - only seven days older than Thomas had been when he'd died - took his own life.

 "He did this because he felt there was no hope that he was going to grow up and have a normal life," Kathy says. “It’s impossible not to feel that we failed Stuart…that we didn’t see this coming”.

"The sadness," she says, "is overwhelming."

 There are days when Kathy asks, "'What did we do?', 'Why does God hate us?' There are plenty of days when we don't want to do this anymore," she tells Freedman. "But quite frankly we don't have a choice."

Kathy doesn't want you to look at her and say, "I don't know how you do it," or "If it were me I would be lying in the corner unable to function." Some days, that's exactly what her life looks like.

Firstly, Kathy gets out of bed because she has purpose. As well as The Thomas Kelly Foundation, the family now have the Stay Kind initiative, in memory of Stuart.

Everyday in Australia, eight people take their lives. Their message is simple; listening saves lives. They promote kindness, compassion and empathy.

LISTEN: You can listen to the full episode of No Filter with Kathy Kelly, here. 

But Kathy's primary, unwavering focus, is their daughter Madeleine. "She's all that we have left," she told Freedman. "I want her to know that she's our prime focus and that the only way we are going to find happiness in our lives again is through her happiness, and through the fact that one day she will meet a nice partner, get married and have children of her own."

Madeleine said to 60 Minutes last month, "Mum and dad deserve to see one of their children grow up."

So, how do you make a devastating story bearable?

Well, in short, you don't. But - as Kathy says - "life doesn't stop".

You put one foot in front of the other, and you work to make meaning out of - not one, but two - senseless and unthinkable tragedies.

If you and I commit to the core values that sit at the heart of Take Kare and Stay Kind - to challenge our drinking culture, to disavow any form of violence, to look out for each other, to listen, and to live with genuine compassion, then Kathy and Ralph Kelly did not lose their sons in vain.

Thomas and Stuart's legacy as two good, kind , empathetic people will live on - and the experiences of the Kelly's is one that Australia will never, ever forget.

 You can visit the Thomas Kelly Youth Foundation here, where you can volunteer or donate.