Four-year-old Henry died unexpectedly in 2015 following complications from pneumonia.

His parents donated Henry's organs to honour his short life, and asked community members to discuss their organ donation wishes with loved ones so they were prepared, should they ever be in that position.

''It was fitting because of the type of person he was and the type of person he was yet to be,'' Mrs Barrett said at the time.

Four years after Henry's death and the Barretts have turned their attention to another life-saving donation: blood.

Henry needed "litres of blood" in his battle with pneumonia and the Barretts have established the 'Honour Henry' blood drive to help draw out more donors.

After donating for the first time, one of Mrs Barrett's friends received a message telling her where her donation had gone and how it had helped someone.

This is the message the Barretts want shared widely.

The Australian Red Cross Blood Service website says one in three of us will need blood products in our lifetime, yet only 3 per cent of us give blood.

Almost 30,000 blood donations are needed nationally each week, but demand for blood and blood products is expected to double within the next 10 years.

Blood donors give whole blood, plasma or platelets, with each donation capable of saving up to three lives.

Raising awareness about organ and blood donations has been an important task for the Barretts, but one of the other realisations that came from Henry's death is how to cope with grief.

Using her own experience grieving for Henry, and her knowledge as a school psychologist, Sarah Barrett has helped many Launceston children who have faced grief and trauma.

Henry lives on in this legacy.