The only way someone can have life insurance on them as the insured person (meaning, the policy would pay the death benefit if that person died) is if they gave their consent to it. So the best place to start is to ask your husband if he signed any applications authorizing someone to take out life insurance on him.
If his parents took out life insurance on him as a child, they may have kept a copy of the policy somewhere, or perhaps you know where they did business so you could ask that office if they have a record of life insurance taken out on your husband.
If he has any through work, they will also have a record.
The first place to look is your husband’s employer group plan to see if he elected life insurance. It may also be itemized on his pay stub or payroll check receipt. It is possible that his employer purchased life insurance on him as a key executive or part of his executive package separate from the businesses’ group plan. The next place to look is your checking account for payments that appear to be to an insurance company.
If his parents took out life insurance on him as a child, they may have kept a copy of the policy somewhere, or perhaps you know where they did business so you could ask that office if they have a record of life insurance taken out on your husband.
If he has any through work, they will also have a record.