If a family member needs special care, you need a complete guardianship solution. The guardian should be such that he/she can take care of your disabled loved one in the absence of a parent. It would help if you had someone skilled at taking care of a special needs child or an adult.
Furthermore, he/she should also have the ability to make sound decisions related to finance and health. However, to ascertain the best possible guardianship, you would be better positioned if you consult a special needs attorney.