Kelly, from Bowral, suffered catastrophic head injuries during  an unprovoked attack from Kieran Loveridge  on July 7, 2012.

Loveridge's  original sentence, handed down by Justice Stephen Campbell on November 7, included four other assaults he inflicted on other young men on the same night.

On Friday, as Kelly's mother cried quietly in court, that sentence was almost doubled. The Chief Justice Tom Bathurst declared Loveridge would serve a non-parole period of 10  years.  

The original sentence generated a furious response from the dead teenagers' parents. The crime   also began a wave of momentum to address alcohol-related violence which resulted in the introduction of strict mandatory sentences in NSW.

The Director of Public Prosecutions appealed the decision, advancing seven separate grounds of appeal, including that Justice Campbell ignored the need to deter others from behaving in the same way.

Speaking outside court, Ralph Kelly said he and his family were relieved.

"It's difficult - there is no celebration today," he told reporters, flanked by his wife and his other son, Stuart.

"You can’t balance a life with years in jail. It’s very bitter sweet as we’re three days away from the anniversary of Thomas’ death."

Speaking about his brother's death for the first time, Stuart Kelly said he had tried to understand why Thomas lost his life but couldn't come up with any answers.

"I miss all the things that brothers do together, throwing a ball, laughing, joking playing,” the 16-year-old said.

"I want Thomas’ short life to see meaning in his death - a culture where we accept responsibility for our actions, and not where we blame on the past  ... It’s totally unacceptable in our society.

"I can tell you first hand that to experience this kind of pain at such a young age is just…it’s just too hard." 

SMH