Social Security Disability is an insurance-based system funded by federal income taxes. There are specific rules about the number of years a person has to work and “pay in” in order to be insured for the disability system. Therefore, the parents of a person between the ages of 18 and 22 are the only family members who have had the opportunity to earn enough income (and pay enough FICA taxes) to be eligible for Social Security Disability Insurance benefits. The DAC benefit is based on the work record (tied to the Social Security number) of the highest-earning parent. Therefore, in order to determine the highest potential DAC benefit amount, the SSA needs to know the Social Security numbers of both parents.