Did he come to the U.S. illegally, or he fell out of status?
This answer is of a general nature and should not be relied upon as final, nor is it intended as legal advice. Consult with a qualified attorney before making any legal decisions. Gen Kimura, (832) 247-6932.
If your fiance and you get married (he will need to be legally divorced prior to you marrying each other); and he came here on a visa and overstayed, he may be able to adjust (fix) his status here in the US. If he didn't come to the US legally, has anyone ever filed anything on his behalf before? You need to speak to an experienced immigration attorney prior to filing anything, because there may be options that are available to him, depending on the circumstances in which he entered the US originally.
What needs to be done depends on how your fiancé entered the US, whether he qualifies for 245(i), etc.
You should retain an experienced immigration lawyer to review all the facts, advise you, and handle the case.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.