Create a Cursor using SQL with all fields from both child files using the union statement. You will require to use dummy place holders for fields in Child A that are not in Child B and vise-versa. Also include an addditional dummy field (SAY 'Source') that indicates which file the data came from. Make sure that the last Order By Parameter is "Source"

In the Report have 2 detail lines. One for child file A and the other for the other child file B. The fields in each line should also have a 'Print When' clause to match the 'Source' field.