"If Thomas had not been killed, Stuart would be here today." The Kellys tell their tragic story.

Content warning: This post deals with suicide.

The Kelly family have experienced more overwhelming grief and loss than any family should ever have to endure.

In July 2012, their eldest son, Thomas, was killed by a one punch attack in Sydney’s Kings Cross. He was just 18 years old at the time.

Then last year, their youngest son Stuart, took his own life.

Within the space of four years, their family of five was down to three. Ralph and Kathy Kelly have opened up to 60 Minutes about losing their two sons, and how they - and their daughter Madeline - are carrying on their legacies.

The Kelly's believe the backlash Stuart received after campaigning for stronger lockout laws, contributed to his decision to take his own life.

"Had Thomas not been killed; Stuart would be here today. Without a doubt," Mrs Kelly said.

In 2015, Stuart made an impassioned speech, calling for the continuation of controversial lockout laws in NSW, in order to tackle alcohol-fueled violence on Sydney's streets.

"Premier will you make this promise tonight? Australia is an alcoholic; we need to rethink the way we drink. Tonight your involvement and your voice can and will make a difference," Stuart said.

However, not everyone was in support of the lockout laws and as Stuart became the face of the movement, he also became a target of constant online abuse and death threats.

"So you copped this simply because you didn’t want another family to suffer as you had because of a drunken coward’s punch?" Langdon asks the Kelly's in the 60 Minutes interview.

"Yeah," Mrs Kelly said. "And we've lost another son because of it."

"How do you ever get over losing two children for absolutely nothing?" she adds.

The Kelly family is determined to honour Stuart's life and they've teamed up with the NRL to raise awareness about youth suicide.

The Thomas Kelly Youth Foundation is launching Stay Kind Day on 23 July this year, to try to curb Australia's youth suicide rates.

The devastating impact of one coward punch. 8.45 SUNDAY on #60Mins | How the same tragedy killed two teenage brothers four years apart. pic.twitter.com/DRSu0lL4mT

— 60 Minutes Australia (@60Mins) July 7, 2017

According to the website, Stay Kind takes its name from Stuart’s initials, just as Take Kare uses the initials of his older brother, Thomas.

The initiative is supported by the NRL, Channel Nine and Lifeline.

"We just saw that voice getting back into the community," Mr Kelly said. "Saying to people - you're not alone if you're suffering from this. You're not a burden on your family, understand that you're loved and that you’re an important person in society."

If this post brings up issues for you, or you just need someone to talk to, please call Lifeline on 131 114. You can also visit the Lifeline website here and the Beyond Blue website here.

Griefline also provides free telephone and online counselling support services to people dealing with mental health issues, suicide, carer support, terminal illness, unemployment, and more.

National: 1300 845 745 (from landlines)

National: (03) 9935 7400 (from mobiles)