You are protected by the ADA if you are discriminated against because of your relationship or association with an individual with a known disability. The reason the ADA prohibits discrimination based on relationship or association is to protect you from job-related discrimination based on unfounded assumptions that your relationship to a person with a disability would affect your job performance, and from actions caused by bias or misinformation concerning certain disabilities.
For example, if you have a disabled spouse and apply for a job, the ADA would prevent you from being denied employment because of an employer's unfounded assumption that you would use excessive leave to care for your spouse. The ADA also would protect you if you do volunteer work for people with AIDS, and as a result had a discriminatory employment action taken against you that was motivated by that relationship or association.