The body of 18-year-old Stuart Kelly was found in his home in Mona Vale last Monday, four years after his older brother Thomas Kelly died following a one-punch attack in Kings Cross.
The memorial service on Thursday at the school's Parramatta campus saw Prime Minister Malcolm Turnbull and NSW Premier Mike Baird pay their respects.
The King School principal, Dr Tim Hawkes, said in a statement. "For Ralph and Kathy [Kelly] to have lost their eldest son Thomas to a coward's punch in 2012 was appalling.
"To have now lost their youngest son Stuart is beyond awful.
"Although both boys had left the school when they died, they were still closely connected to the King's 'family'. Therefore, we are in deep grief."
Stuart was 14 when his brother Thomas died after being randomly punched while walking with his girlfriend in Kings Cross in July 2012.
Following his brother's death, Stuart went on to campaign heavily against alcohol-fuelled violence, and support the work of the Thomas Kelly Foundation.
The campaign, coupled with the death of one-punch attack victim Daniel Christie in 2013, eventually led to the controversial lockout laws being introduced by the NSW government the following year.
Principal Dr Hawkes said the school would continue to support the Kelly family in every way possible.
If you would like support, please phone:
Suicide Call Back Service 1300 659 467
Lifeline 13 11 14
Mensline 1300 789 978
Kids Helpline 1800 551 800
Beyondblue 1300 224 636.
Mensline 1300 789 978
Kids Helpline 1800 551 800
Beyondblue 1300 224 636.
