UNLIMITED FAMILY-BASEDImmediate Relatives of U.S. Citizens (IR): The spouse, widow(er) and unmarried children under 21 of a U.S. citizen, and the parent of a U.S. citizen who is 21 or older.
Returning Residents (SB): Immigrants who lived in the United States previously as lawful permanent residents and are returning to live in the U.S. after a temporary visit of more than one year abroad.
LIMITED FAMILY-BASEDFamily First Preference (F1): Unmarried sons and daughters of
U.S. citizens, and their children, if any. (23,400)
Family Second Preference (F2): Spouses, minor children, and unmarried sons and daughters (over age 20) of lawful permanent residents. (114,200) At least seventy-seven percent of all visas available for this category will go to the spouses and children; the remainder will be allocated to unmarried sons and daughters.
Family Third Preference (F3): Married sons and daughters of U.S. citizens, and their spouses and children. (23,400) http://travel.state.gov/visa/immigrants/ty...types_1306.htmlFamily Fourth Preference (F4): Brothers and sisters of United States citizens, and their spouses and children, provided the U.S. citizens are at least 21 years of age. (65,000)
You need to first become a citizen through naturalization, then you can file a petition for a F3 visa for married children. the wait for a visa number for F3 visa is quite long 5 or more years from date of filing, currently USCIS is processing applications dated April 2001