A U.S. citizen who is at least 20 years old can petition their parent, and in some circumstances their stepparent, to live in the United States. For a stepparent, the marriage between their parent and their stepparent must have occurred before the U.S. citizen was 18 years of age. In order to apply a separate petition would have to be made or each parent or stepparent, and then they would either be processed abroad in their country or through a process called adjustment of status in the United States if, in fact, they’re here.