As Robbie Powell lay dying in hospital, his father William says he promised his son he would find out the truth.
Robbie would have been 24 this year
But it took Mr Powell and his wife Dianne 14 years to witness an inquest into what had led up to their son's avoidable death.
Friday's verdict follows a series of court appearances and three police inquiries.
After a long inquest, the Swansea jury decided Robbie died from natural causes - aggravated by neglect.
His father William has described what happened on Robbie's last day - and the promise he made to his child as the boy lay unconscious in Swansea's Morriston Hospital.
"I had to carry Robert into the hospital after being refused an ambulance," said Mr Powell from Ystradgynlais.
"When we got there I had to lay him on the bed and there was panic, I watched him take his last conscious breath, it was the most difficult time of my life.
"Robbie went into intensive care, we saw him after that and he had passed away.
"We saw him in a little room and that's when I made that promise to him."
Mr Powell added: "He had a high regard for me, irrespective of what I am, he thought I was wonderful and I miss that."
Robbie's headmaster Ogwyn Phillips, of Ysgol Cynlais, remembers the devastating impact of his death on the school.
"He was the third in the family at the school and he followed in the same vein as the brothers, he was very honest, very likeable and worked diligently.
"He gave his best to all school activities, he was a solid all-rounder."
A tree was planted in Robbie's memory at the school.
Local councillor Betty Rae Watkins remembers Robbie was a "happy boy".
"I knew him by sight, he stood out - he was happy, he beamed," she said.
Coun Watkins added: "This is a nightmare for the family.
"It's become very intense and it is very sad for the family.
"It is a nightmare for the medical profession, it's a nightmare for all," she said.
Events surrounding Robbie's final weeks and hours have been scrutinised by the jury at the inquest which opened in February 2004.
A series of witnesses each offered their insight into the weeks and months leading up to Robbie's death on 17 April, 1990.
The court heard how Robbie had fallen ill shortly before Christmas 1989 with sickness and stomach pain.
William Powell made a promise to his dying son
After being seen by a family doctor, Robbie was taken to Morriston Hospital where he was treated for four days.
A hospital consultant ordered a test which would have picked up Addison's disease - a rare but treatable hormonal condition.
But the inquest jury heard that the test was never carried out.
On 18 January 1990, Robbie had a check-up in hospital and it was thought he had had gastroenteritis.
But on 1 April Robbie became ill again.
Over the next two weeks, he was seen seven times by five family doctors. None of them realised that he might have Addison's disease.
Robbie's condition deteriorated so much, he suffered two heart attacks and died.
It was after the post mortem, the family first heard of Addison's Disease, and their fight began.
In 1996, the former West Glamorgan Health Authority admitted liability for Robbie's death.
But although £80,000 was paid into court, there were further legal arguments and the Powell family never received compensation.
In April 2003, the Crown Prosecution Service said no charges would be brought agains the five GPs involved in caring for Robbie before he died.
"Nothing is going to bring Robbie back but we have known that since the night he died," Mr Powell has told BBC Wales.
"From somewhere I have had the strength - whether it's for the love of Robbie or for other reasons, I don't know.
"My wife and I have stuck together to see this to the end no matter what the cost is."
Mr Powell said in the early years following his son's death he locked himself in a room with documents and records.
"I am sure at that time I came close to having a nervous breakdown, it was a very difficult time initially," he said.
Ten years after the Powells first asked for an inquest and after an appeal to the attorney general, they were finally told, in December 2000, that there would be an inquest.
It took another four years for that to take place - now their fight for a public inquiry begins.