distinct group_concat

Summary

How to get a group concat to only show distinct values?

Content

Hello,

I have a parent table with two children tables (siblings).  I need information from one child table summed and information from another child table group concatenated.  I have the report working as intended, however, the group_concat function is repeating the values for child table 2, once for each member of child table 1 even though child table 1 is only represented in the report using a Sum function.

How do I get the duplicate group_concat values to be eliminated? In otherwords, I want the group_concat function to only show unique values.  I've tried distinct and first and last without success.