Does she have an account that is in her name or does she get a check from Social Security or a pension, retirement of any kind? If so she can pay you from her funds. If this is what you do have a caregiver agreement that will spell out whet you do and the amount you will get paid. And since you should not do all this yourself other caregivers that are hired should also be paid from her funds.
But if she’s his wife, they probably use both incomes ( pension and SS checks) to LIVE and pay bills. How would this compensate her husband if they live together as man and wife? I’m confused.
https://www.agingcare.com/articles/how-to-get-paid-for-being-a-caregiver-135476.htm