The U-1 visa is a nonimmigrant visa which is set aside for victims of crimes (and their immediate family members) who have suffered substantial mental or physical abuse and are willing to assist law enforcement and government officials in the investigation or prosecution of the criminal activity. Subtypes of this visa are U-2 issued to spouses of U-1, U-3 issued to children of U-1, U-4 issued to parents of U-1 under the age of 21 and U-5 issued to unmarried siblings under the age of 18 of U-1 who is under 21.