Children and the K1 Visa
Your fiancée may already have children that he or she wishes to bring to the US. If these children are under 21 years of age and are not married, you and your fiancée must obtain a K-2 visa for each child who will relocate. Remember that children are not automatically approved to relocate and pursue a green card in the US just because your fiancée’s K1 visa is approved.
You must apply for a K-2 visa for each child after obtaining approval on Form I-129F, petition to bring a foreign fiancée to the US. You must list any children who will immigrate with the parent on the K1 visa form. Keep in mind that you will need to pay application fees for each K-2 visa, as well as fees for medical examinations, vaccines, and travel costs for children who will also immigrate and pursue the K1 visa.