one way to do this without passing more than 1 parameter is to place the summary in a sub report and reveal that sub report with the push of a button. Unfortunately sub reports in footers are buggy in access so you have to filter the sub report manually.
we start with a similar simple normalized database:
Then I added a simple form with a multi-select listbox of families and a button to open a filtered report.

Private Sub cmdSearch_Click()
'Build Filter for report
Dim strFilter As String
Dim firstselectedfamily As Boolean
firstselectedfamily = True
For i = 0 To lstFamilys.ListCount - 1
If lstFamilys.Selected(i) = True Then
If firstselectedfamily = True Then
strFilter = "FamilyFK = " & lstFamilys.Column(0, i)
firstselectedfamily = False
Else
strFilter = strFilter & " OR FamilyFK = " & lstFamilys.Column(0, i)
End If
End If
Next i
'open report with filter
DoCmd.OpenReport "ExampleReport", acViewReport, "", strFilter, acNormal
End Sub
here is the ExampleReport with a button to show a summary of duplicates:

The button reveals the hidden sub report based on a query that finds the duplicates:

The duplicates query is made by grouping based on family and test where both the count of familyID and TestID is at least 1:
Normally the summary report would be linked to the main report by a master child relationship, but the summary looks natural in the main reports footer where sub reports happen to be bugged and do not filter correctly. To get around the bug we provide code to filter the summary report:
Private Sub cmdSummary_Click()
'filter summary form by using the main reports filter
Me.subfrmSummary.Report.Filter = Me.Filter
Me.subfrmSummary.Report.FilterOn = True
Me.subfrmSummary.Requery
'show/hide summary form
If Me.subfrmSummary.Report.Visible = False Then
Me.subfrmSummary.Report.Visible = True
Else
Me.subfrmSummary.Report.Visible = False
End If
End Sub
Again, to get around the bug do not link the sub report to the main report with a master/child relationship. Instead set the filter with code.