Birth certificates showing place of birth for every family member, current passports, marriage and any divorce records, and evidence of prior immigration filings that might already carry a priority date. If alternative chargeability is being considered, the documents establishing the qualifying family relationship become central to the analysis.
Check the birthplace field before anything else
Passport data pages sometimes record a city rather than a country, or a place whose sovereignty has changed since the holder was born. Both create questions worth resolving early with the birth certificate and, where needed, a certified translation. Keep the family's records together in one set, because chargeability is assessed per person even though derivatives usually follow the principal.
Note any prior petitions that could preserve an earlier priority date. Resolve the birthplace question before anything else, because it determines the queue. Passport data pages sometimes record a city rather than a country, or a place whose sovereignty has changed since the holder was born, and the birth certificate with a certified translation settles it.
Collect birth certificates for every family member, current passports, marriage and any divorce records, and evidence of prior immigration filings that might already carry an earlier priority date worth preserving. Keep the family's records together in one set, since chargeability is assessed per person even though derivatives usually follow the principal. Note any earlier filing explicitly, so it is not overlooked when the file changes hands.