Site: nolo.com
... member for immediate or expedited U.S. citizenship, that person might then be able to sponsor (file an I- ... Section 319(e), 8 U.S.C. Section 1430(e).)
Surviving Family Members of U.S. ... Section 319(d), 8 U.S.C. Section 1430(d). Also see Who Can Apply for U.S. ... Section 329, 8 U.S.C. Section 1440-1.)
Who should file the application? ... Note, however, that there's a time limit on applying: You'll need to file a petition using USCIS Form I- ...