You should consult an attorney licensed in the state where your husband's father lived. There may be a challenge to the will based on incapacity or undue influence, but those are difficult to prove. Is the will being probated? Has your husband received notice as an heir. You could also call the probate court to check on the proceedings.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on since each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.