Not all family relationships serve as a basis to apply for lawful permanent resident status. There are two basic categories Immediate Relatives and Preference relatives.
Spouses, parent or unmarried minor children (under 21) of U.S. citizens. This category includes marriage based cases. There is no quota for this category as visas are immediately available.
Preference Relatives, in which cases are based on a quota system, are set as follows:
1. First Preference
a. UNMARRIED SONS AND DAUGHTERS OF U.S. CITIZENS. Adult children of US citizens or those who have reached the age of 21 years prior to issuance of the immigrant visa.
2. Second Preference
a. SPOUSES, SONS AND DAUGHTERS (Unmarried and under 21 years of age) OF LAWFUL PERMANENT RESIDENTS;
b. UNMARRIED SONS AND DAUGHTERS, OVER 21 YEARS OF AGE, OF PERMANENT RESIDENTS
3. Third Preference
a. MARRIED SONS AND DAUGHTERS OF US CITIZEN.
4. Fourth Preference
a. BROTHERS AND SISTERS OF US CITIZENS.