Guardianship
In New York State, when a person becomes 18 years old they are assumed to be legally competent to make decision for themselves. This means no other person is allowed to make a personal, medical or financial decision for that individual. If a person is "intellectually disabled or developmentally disabled," has difficulty making decisions for themselves and over 18 years old, you can ask the Surrogate's Court to appoint a guardian for him or her.
Brandow Law Guardianship Workshop