Based on the grounds on which the application is submitted, the requisite documentary documentation will vary. The required documentation requires documentation of the EEA national and non-EEA national applicant's ID, proof of engagement, and evidence that the EEA national is a "qualified person" (if in the United Kingdom). It is not necessary to extend a family visa; you would need to apply for a residency card while in the United Kingdom. Of note, it is still possible to apply for an EEA Family Permit UK from overseas again, if necessary. For a term of 6 months, the family visa is given which requires the holder to fly to the UK.