I have some legacy data in a flat file that I want to import to a geodatabase where I have a 1:m feature class with related tables. Some records in the flat file will be appended to the feature class while other fields form records in a related table. What is the best way to accomplish this since new records imported into the FC will populate with a new GUID that will need to find its way into the related table's "parent GUID" when related records are added?