You cannot file an immigration petition for your wife’s parents. If you are a US citizen, you can only sponsor Green Cards for your spouse, parents and your children. However, you can also help other categories of relatives to obtain Green Cards and you may file petitions for your married and unmarried children above age 21 and your siblings.
Nevertheless, your wife can sponsor her parents after she becomes a US citizen. If your wife currently holds a conditional Green Card, you and your wife must jointly file an application to remove conditions on that card. After the immigration interview, if the USCIS officers find that your wife is eligible for lawful status and that your marriage is not fraudulent, your wife will be issued a ten year Green Card.
After remaining in the country as a Green Card holder for three years, your wife can apply for US citizenship, by filing the naturalization application, Form N-400. However, you and your wife must still be married at the end of the three year period and your wife must meet a few other prerequisites, to file Form N-400.
To file an application for naturalization, the spouse of a US citizen must not be a minor and must be above age 18. She must have been a lawful resident of the country for a three year period or more. She must have lived in the American state where she files her application for citizenship, for at least three months. Moreover, she must not leave the United States after filing her application and must remain within the country until she becomes a naturalized US citizen.
Applicants who file their naturalization applications will be required to appear for the naturalization interview. Hence, she must prepare for these tests and must demonstrate that she can read, write and speak English. Similarly, the applicant’s knowledge of US history will also be tested.
If your wife satisfies all the requirements, she can apply for US citizenship after residing in the country for a three year period as a permanent resident. After she becomes a US citizen, she can sponsor her parents for lawful status in America, within three or four months from the date of becoming a US citizen.