Dependents of a continuing F1 student, previously admitted into the U.S. in F2 status should have a current Form I-20 in their names that certifies admissibility (i.e. DSO signature approving travel). Note each dependent must have an individual Form I-20. Besides, a valid visa unless you are from Canada or Bermuda, the primary (F1) must be in active status. Also, the F1 holder must have a valid Form I-94 arrival/departure card.