You really need to find an immigration attorney here on Avvo with the Find a Lawyer tool. Immigration law is complicated and you need assistance. It is not a do-it-yourself project.
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You and your husband will both need file i-864's - for both your mother and father. Hiring an attorney can save you months of wasted time due to mistakes.
Yes you are correct. You need to file I864 - one form for each parent and your husband can file I864A if you live in the same household and file joint tax returns.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.