The Immigration and Naturalization Service has many categories for permanent residents. You must fit into one of those categories to be eligible for a green card. There are often preferences and quotas within categories. There is no quota limit on the number of green cards that can be issued to immediate relatives of U.S. citizens. Preferences Those who receive green cards under categories with quotas fall into one of several classifications called preferences.
Preferences give priority to certain individuals over others who apply for green cards.
Family Preference Green Cards Family first preference. Unmarried people, any age, who have at least one U.S. citizen parent. Family second preference. Family third preference. Married people, any age, who have at least one U.S. citizen parent.