US Residency or green card for step children of American Citizens
If you are the child of a step parent who has US citizenship and the marriage that created that step child-step parent relationship occurred prior to your eighteenth birthday and you are under twenty-one years of age, you can obtain residency as the immediate relative of your step parent. This is a very important consideration because it does not depend on the status of your natural parent. Your natural mother or father could be in the United States without permission, unlawfully, or unable to obtain any benefit through their marriage to the US citizen. But the child of that foreigner, the child of that natural parent could obtain status as a legal permanent resident. If you are over twenty-one years of age but the relationship that established your relationship to that step parent, if the marriage occurred before your 18 birthday, you will always be considered the son or daughter of that US citizen. The Us citizen could apply for your legal permanent resident status, the only difference is if you are over twenty-one year of age you will have to wait until a visa becomes available which can be several years.