Supplemental Security Income (SSI) is a benefit that is provided by the federal government for children under the age of 18 years old who meet the qualifications for disability and for disabled people over the age of 18 years old who still depend on others for their care. SSI makes monthly payments to people with limited income who are over the age of 65, blind or disabled. For the Down syndrome child to qualify, he or she must have limited income, resources, and meet the definition for disabled by the federal government.