In time the world came to know wee Oscar and his battle against a cruel disease.
So, too, Leona and Stephen, his loving mother and father who have endured every parent's worst nightmare.
Through the heartache and trauma of their son's battle for life, their bond remained strong.
The couple met after being introduced by mutual friends on St Patrick's night in 2001.
They married five years later in December 2006 and settled in east Belfast.
Just over a year later Leona became pregnant.
When Oscar was born on September 10, 2008 the young couple's life seemed complete – but their dreams were soon shattered.
Leona and Stephen became concerned about Oscar's development. He was later diagnosed with Jacobsen syndrome, an extremely rare chromosome disorder said to affect just one in every 100,000 people.
Oscar made astonishing progress and eventually was on par with other children his age.
He started playgroup in September 2011 – two days after his third birthday.
However, over the next two months Oscar was in and out of hospital.
Something was wrong – but the devastating news that followed must still have come as a bombshell to Stephen and Leona.
Oscar was diagnosed with high-risk neuroblastoma, a rare children's cancer which affects one in every 100,000 children.
Oscar beat the odds to pull through and, at one stage, appeared to have beaten the cancer, which threatened to cut his life short.
But in a cruel twist, the little boy became ill for a second time last August.
Sadly, this time – and despite a heroic fight – it was a battle too far.
Last month Stephen and Leona made the heartbreaking decision to move Oscar into the care of the Children's Hospice.
Leona revealed he was suffering agonising pain and had been "going through hell".
His suffering was so great that he told his parents: "I don't want to be a boy any more."
In what would be the final update to the online diary documenting Oscar's fight, Leona wrote: "In the past four weeks Oscar has suffered more pain than we could have imagined, and more anguish than any five-year-old should ever know."
Even in his final weeks, as Oscar fought for life, he refused to give in. His parents were told by one doctor: "Your son doesn't do giving up."
The fighting spirit which Oscar has shown is a lesson to everyone. And so, too, the courage and strength of his remarkable parents.
Donations to raise money for the Northern Ireland Children's Hospice in memory of Oscar can be made via a dedicated JustGiving page at justgiving.com/oscarknox.