No. Hunter Brown does not have Down Syndrome. Dayton Brown, Robyn's son, has Asperger's Syndrome.

See the link below:

Hunter - 1976 The Lysenko Syndrome 1-3 was released on:

USA: 4 March 1977

If a person is severely affected by Hunter's syndrome, life expectancy is about 10 to 20 years. However, some people with the disorder life an almost normal life span.

The severe form is associated with progressive mental retardation and physical disability, with most individuals dying before age 15. Males with the mild form of Hunter syndrome usually have normal or near normal intelligence