The Parents of a Fiance Visa beneficiary can obtain an Immigrant visa and their US legal permanent residency once their child becomes a US Citizen. This process takes about three years or more. Once the fiancee enters the United States using his or hers K1 Fiance Visa, and then gets married, the next step is to apply for Legal Permanent Residency. This process takes about 4-5 months. Then after three years as a Legal Permanent Resident, the foreign spouse can then apply for US Citizenship. Once the foreign born spouse becomes a US Citizen (the person who originally came into the US on a Fiance Visa), he or she can apply for an Immigrant visa for his or her parents.
Parents of US Citizens are considered immediate family and therefore are not subject to any of the limitations and caps on immigration. This means that the US Citizen child over the age of 18, may petition to bring his or her parents to the US at any time. The US Citizen child over the age of 18 starts the process by filing a petition to bring his/her foreign national parents to the US. The process differs depending on the location of the parents at the time of the petition filing. If the parent is in the US and had entered the US legally (inspected by an immigration officer at customs) the request for Adjustment of Status can be filed contemporaneously with the Petition for Alien Relative. If the relative is abroad, once the petition is approved, the process continues through the NVC (National Visa Center) and then on the consulate or embassy abroad.
Either way, the parents of a US Citizen child who is over the age of 18, can obtain an Immigrant visa to come to the United States as a Legal Permanent Resident.