Two Sydney parents have been charged with the manslaughter of their diabetic six-year-old son, who died after attending a "self-healing" course where he was allegedly deprived of insulin and food.

Emergency services found the Year 1 student unconscious and not breathing at the Ritz Hotel in Hurstville on April 30, 2015, after the boy had left the workshop held at a nearby clinic. He died at the scene.

Hongchi Xiao, the "healer" who treated the six-year-old boy.

Police on Tuesday arrested the boy's father, 56, and mother, 41, at their home in Prospect in Sydney's west and took them into custody, alleging their "gross negligence" caused the boy's death. Authorities believe the parents were complicit in the deliberate denial of food and medicine.

But the man who ran the $1800 week-long course continues to elude police in Australia as well as Britain, where he was recently detained on suspicion of manslaughter over another death.