The U.S. immigration system allows U.S. Citizens and Lawful Permanent Residents (LPRs) to sponsor close relatives so that they may immigrate to the United States. A family-based immigrant visa application will allow your family members to move to the United States and live/work here indefinitely.
The number of family visas available annually is unlimited for certain immediate relatives of U.S. citizens, but capped for the relatives of U.S. Lawful Permanent Residents (LPRs) and the more extended family of U.S. citizens.