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Having worked illegally in the U.S. is not going to get him his green card revoked. However, if it can be proven that he ONLY married her for the green card, then he can be permanently deported so that not even a real marriage to another U.S. Citizen nor even having U.S. Citizen children would save him.
18 U.S.C. § 1325(c), provides a penalty of up to five years imprisonment and up to $250,000 fine for any "individual who knowingly enters into a marriage for the purpose of evading any provision of the immigration
Of course this would apply to your daughter as well, but only if she was involved in the fraud.
If you believe you have enough evidence, you can make the report by going to www.ice.gov and calling the 866 number at the top right of that page or clicking the link there.
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