Is there anything he or they could do to get his citizenship so they can be able be together as a family in the US?

*Consulate Processing* Consulate Processing must be completed. This allows the petition to first be sent to the National Visa Center, and then the appropriate documents and package to go to the U.S. Consulate or Embassy. If done correctly, you will be able to enter as a Lawful Permanent Resident and will be in the U.S. in less than one year. Of course the time might be a bit less or more depending on the backlog of the U.S. Consulate or Embassy and whether or not a Waiver of Inadmissibility is needed. Attorney Fees (Filing Fees and Costs not included).

Your cousin can petition for her fiance, but she must either be married to him first or file for a fiance visa and marry him when he enters the U.S. I strongly suggest that your cousin contact an experienced immigration attorney for a face-to-face consultation and give him/her all of the facts surrounding her situation. He/she would then be in a better position to analyze her case and advise her of her options.

If the father has never had issues with US immigration, then your cousin can petition for him as her fiance to come to the US or they can get married and she can petition for him as her spouse. In either case, the process will take about 9-12 months if he is not otherwise inadmissible to the US.

Your cousin and fiancee should get married in Mexico and then your cousin needs to file an I-130 with USCIS. Once the I-130 is approved her fiancee needs to go through the visa interview process at the US Consulate in Juarez. Depending on her financial situation she may need a co-sponsor at that point.

Your cousin will need to submit an I-130 petition on his behalf to get the process started after they have been married. If he enters the US legally, he can also apply for adjustment of status on form I-485.