I have found contradictory information online to my previous post:
10. Am I required to have my own passport to apply for K-2 visa?
In general, a separate passport is not required if you are below the age of 16. If the Consulate requires you to have a passport, it will be listed on the checklist."
http://faq.visapro.com/K2-Visa-FAQ4.aspSome more information here:
"All children (under 21 years old and unmarried) of an alien classified K1 should be listed on I-129F Petition for Alien Fiance(e). Children also must be present at the interview."
http://moscow.usembassy.gov/consular/consu...cord_id=fiancee"Accompanying child requires a valid passport (or may be included in the parent's passport), a birth certificate and a medical examination. If a child is 16 years of age or over, police certificates are required. Translations of the indicated documents are required as well."
http://www.usembassy.ru/consular/consular....cord_id=fianceeHope that solves the issue for you.