1. Insert a Group on a field to represent each Constituent (SortKey, BioName, etc..).

2. Insert a Summary/DistinctCount of a field to represent each Proposal (Proposal Name, etc..).  For the Summary Location within the 'Insert Summary' dialog box, select the Group (created in step 1 above) that represents each Constituent.

3. From main menu select Report>Selection Formulas>Group and put in the appropriate formula like below:
          DistinctCount ({CnPrProp_1.CnPrProp_1_Proposal_Name}, {CnBio.CnBio_Name}) > 1

Note that the formula above in step 3 is telling the report to only show those records/groups where the DistinctCount summary value of the Proposal Name is greater than 1.