You cannot petition for your stepfather because you were over the age of 17 when your parents married. However, if your mother is a US citizen or lawful permanent resident, she can petition for your father instead. But since your father entered the US illegally, he is not eligible for adjustment of status and must return to Mexico for his immigrant visa interview at the US Embassy/Consulate in Cd. Juarez. Based on the information given, he may be subject to the 10-year bar because he was unlawfully present in the US in excess of one year. However, it appears as if your father may be eligible to apply for a provisional waiver of the 10-year bar based on extreme hardship to his spouse/your mother (if she has legal status) and get a decision from USCIS even before he departs the US for his visa interview. In other words, if USCIS approves his application for a provisional waiver, he should have no problems returning to the US with an immigrant visa after his interview.
Answered on Feb 20th, 2015 at 11:13 AM