Sebastian was diagnosed with Wilms' Tumour in 2001
Building work is due to begin on a holiday care home for sick children near Basingstoke, that was the dream of a nine-year-old boy who died of cancer.
Sebastian Gates, of Ascot, Berkshire, died of Wilms' Tumour in 2003.
It was his wish for a home to be built for other sick children to spend time with their families free of charge.
His family will take part in a turf-cutting ceremony at the site of the new home in North Waltham, Hampshire, on what would have been his 16th birthday.
About 180 guests, who have all played a part in the home being built, will be invited to dig a square of turf.
Sebastian's father Michael Gates said it was great to have finally reached this stage.
"It will be a momentous occasion," he said.
"It's taken seven years, during that time we've had our ups and downs, but we've finally got there.
"We now know it's actually going to be a reality rather than a dream."
He added the building of the home was a "muted celebration tinged with sadness".
Fundraising for the house has taken more than six years
"Our son would have been 16, and obviously that's at the forefront of all of our minds.
"It will be a difficult, tough day, but on the other hand it's one we've all been looking forward to."
Plans by Sebastian's Action Trust to build the home were backed in September 2008, but red tape meant there were delays in work getting under way.
The £850,000 self-catering accommodation will include an indoor swimming pool, games room, library and sensory room.
Sebastian was diagnosed with the rare form of childhood cancer in 2001.
Over the next two-and-a-half years he had 12 operations, a stem-cell transplant, chemotherapy courses and radiotherapy but died in 2003.
Sebastian Gates was diagnosed with Wilms' Tumour in 2001 and died in 2003