Can a husband and wife both be on Medicaid?

Yes--both husband and wife can both receive Medicaid assistance. The state they live in most likely has many different Medicaid programs--each with their own eligibility rules. So, my recommendation would be to help them contact the Senior Information & Assistance/Aging & Disability Resources in their area, and they can be screened for services, or referred to the appropriate person for help in determining their eligibility.
I agree with OldBob1936- it's always smart to have an attorney help with Medicaid Planning if an individual or couple has assets like a house, property, cars, investments, life insurance, etc. to know their state's Medicaid rules about Estate Recovery.

Of course. They both would have to have no more than $2000 in countable assets...see your social worker at the county. Also smart to work with a qualified lawyer on this with such issues as house, car, etc.
Grace + Peace
Bob