There are a few different ways that two unmarried people can be on the same health insurance. The first way is if they are both employed and their employer offers family health insurance coverage. In this case, they would both be able to enroll in the employer's health insurance plan. Another way is if one person is enrolled in a health insurance plan through the ACA Marketplace and they add their domestic partner as a dependent. This option is only available in states that have expanded Medicaid coverage. Finally, some private insurers offer family plans for unmarried couples, but these plans are not typically available through the ACA Marketplace.
If you're looking to get health insurance coverage for yourself and your partner but you're not married, there are still options available to you. Employer-sponsored plans and private insurer family plans are two possible routes you can take. You may also be able to add your domestic partner as a dependent on your ACA Marketplace plan, but this option is only available in certain states.