public void Delete( 
   Table relationshipTable,
   KnowledgeGraphRelationshipDescription relationshipDescription
)

{
  var mv = MapView.Active;
  await QueuedTask.Run(() =>
  {

    var edit_op = new EditOperation()
    {
      Name = "Delete a Relationship record"
    };

    //We are  going to use mapmembers in this example
    //we could equally use feature classes/tables
    var kg_layer = mv.Map.GetLayersAsFlattenedList()?
                  .OfType<ArcGIS.Desktop.Mapping.KnowledgeGraphLayer>().First();

    //entities
    var entityOrg = kg_layer.GetStandaloneTablesAsFlattenedList()
                    .First(child_layer => child_layer.Name == "Organization");
    var entityPerson = kg_layer.GetStandaloneTablesAsFlattenedList()
                    .First(child_layer => child_layer.Name == "Person");

    //Relationship
    var rel_stbl = kg_layer.GetStandaloneTablesAsFlattenedList()
                    .First(child_layer => child_layer.Name == "HasEmployee");

    // get the origin, destination records
    Guid guidOrigin = Guid.Empty;
    Guid guidDestination = Guid.Empty;
    using (var rc = entityOrg.Search())
    {
      if (rc.MoveNext())
        //Use the KnowledgeGraphPropertyInfo to avoid hardcoding...
        guidOrigin = rc.Current.GetGlobalID();
    }
    using (var rc = entityPerson.Search())
    {
      if (rc.MoveNext())
        //Use the KnowledgeGraphPropertyInfo to avoid hardcoding...
        guidDestination = rc.Current.GetGlobalID();
    }

    var rd = new KnowledgeGraphRelationshipDescription(guidOrigin, guidDestination);
    edit_op.Delete(rel_stbl, rd);
    edit_op.Execute();//Do the delete
  });
}