The K nonimmigrant classification historically is used for a fiancé(e) (K-1) and his/her unmarried children under age 21 (K-2) of a United States citizen. After December 21, 2001, the K category was extended to include the spouse of a citizen (K-3) and his/her unmarried children under age 21 (K-4).
K-1 visa

The U.S. citizen fiancé(e) must submit a petition to USCIS showing that:

1. S/he and his/her fiancé (e) have physically met within the two years preceding the date the K petition is submitted. This “previous meeting” requirement may be waived in cases of extreme hardship or where such a meeting would violate strict and long-established customs of the beneficiary’s culture or social practice, such as where marriages are traditionally arranged by parents of the bride and groom and the couple are prohibited by custom from meeting before the wedding day; and,
2. Both the U.S. citizen and the fiancé/e must be “free to marry” meaning that any and all prior marriages have been legally terminated; and,
3. Both must intend to marry within 90 days of admission to the U.S. under K status. Once USCIS approves the petition, the Department of State will forward the petition to the U.S. consulate abroad where the fiancé (e) applies for the visa.

K-2 visa
Unmarried child under age 21 of the K-1 may be issued K-2 visas. Proof relationship to the K-1 parent is required. In some countries, evidence that the biological parent has provided his/her consent for his/her child to depart the country is required.
K-1 and K-2 visas are valid for only 90 days for one entry. During this time, the K-1 and K-2 must enter the United States and, during the next 90 days, the K-1 and the U.S. citizen must marry. Thereafter, an application to adjust status to Conditional Lawful Permanent Resident is submitted to the local USCIS office having jurisdiction over the place of residence of the K-1/K-2 in the U.S.
K-3 visa

The U.S. citizen spouse must file both a fiancé(e) petition and an immigrant visa petition with USCIS on behalf of the alien spouse. The fiancé(e) petition must be approved (same requirements as for K-1) and the visa processed through the U.S. Consulate abroad.
K-4 visa

Unmarried child under age 21 of the K-3. K-3 and K-4 visas are issued for a validity of two years. A K-4 can be admitted for up to two years or his/her 21st birthday, whichever occurs first. Extensions of status may be submitted, provided an application for adjustment of status has been filed. An adjustment application can be filed only after the immigrant visa petition has been approved.

Note:  In order for the K-4 child to immigrate to the U.S. with her/his biological parent, the marriage creating the step-child relationship with the U.S. citizen spouse must have occurred prior to the child’s 18 the birthday. However, a child over age 18 but under 21 may still qualify for an H-4 and, subject to immigrant visa quota limitations, immigrate to the U.S. through a petition by his/her biological parent who has since immigrated through the marriage.
Other considerations

A K nonimmigrant may not change status to any other non-immigrant classification.
This information is intended for clients of Jackson & Hertogs only. This is not intended to provide legal advice to non-clients of this firm. Nor will we respond to inquiries from non-clients. You should seek your own legal counsel in these matters.