If you are a qualified K-3 nonimmigrant visa applicant, your child may be eligible for a K-4 visa.  USCIS will allow your child to accompany you if he or she is 21 years of age or under, and is unmarried.  Additionally, for the children of the non-citizen parent to be eligible for the K-4 U.S. visa, the parent’s marriage to the petitioning U.S. citizen spouse must have occurred before the child(ren) were 18 years of age.