Start by reading the guides:
http://www.visajourney.com/forums/index.ph...&page=ussibhttp://www.visajourney.com/forums/index.ph...p;page=ussibpetNote a sibling is 4th preference for immigrant visas, and can take up to 10 years to get a visa number.
QUOTE
LIMITED FAMILY-BASED
Family 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)
Family 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)
http://travel.state.gov/visa/immigrants/ty...types_1306.html