Until you actually arrive in US with the immigrant visa, your stepmother petitioner can cancel the petition she filed for you even if it has been approved. Apart from trying to persuade her otherwise, there is not much else you can do because under the law, the petitioner has the right to withdraw from the petition. Your father must immediately file a Form I-130 petition for you. If approved, you can come to the US based on his petition.
Answered on Jul 03rd, 2014 at 12:40 PM