U.S. immigration regulations mandate how many family members may enter the United States each year based on their relationships to U.S. citizens and a formula that takes into account the previous years' visas, as of 2015, notes the American Immigration Council. Other regulations control employment-based immigration, such as the rules regarding temporary work visas and permanent immigration based on employment.
U.S. immigration regulations state that there is no limit on immediate relative visas, though applicants must be spouses, unmarried children under the age of 21 or parents of U.S. citizens, states the American Immigration Council. Regulations also allow for a limited number of visas for other family members of U.S. citizens under a preference system that favors adult children and siblings, as well as spouses and unmarried children of legal permanent residents. In order for a sibling to be eligible for this visa program, he must be at least 21 years old.
U.S. immigration regulations allow for more than 20 types of temporary worker visas, intended for those not seeking permanent immigrant status, according to the American Immigration Council. Many of these visas are for skilled workers only and, in most cases, include sponsorship by an employer for a specific job offer. Preference for permanent work visas is also based on skill level, with the highest preference going to people who are skilled in categories such as arts, sciences, business or athletics and those who have advanced university educations.