diff --git a/frontend/src/app/components/wp-fast-table/builders/modes/hierarchy/hierarchy-render-pass.ts b/frontend/src/app/components/wp-fast-table/builders/modes/hierarchy/hierarchy-render-pass.ts
index 5b34b8b41f..149d14e3d5 100644
--- a/frontend/src/app/components/wp-fast-table/builders/modes/hierarchy/hierarchy-render-pass.ts
+++ b/frontend/src/app/components/wp-fast-table/builders/modes/hierarchy/hierarchy-render-pass.ts
@@ -115,11 +115,14 @@ export class HierarchyRenderPass extends PrimaryRenderPass {
 
       if (inTable) {
         // Get the current elements
-        const elements = this.deferred[parent.id] || [];
+        let elements = this.deferred[parent.id] || [];
         // Append to them the child and all children below
         let newElements:WorkPackageResource[] = ancestorChain.slice(i + 1, ancestorChain.length);
         newElements = newElements.map(child => this.wpCacheService.state(child.id).value!);
-        this.deferred[parent.id] = elements.concat(newElements);
+        // Append all new elements
+        elements = elements.concat(newElements);
+        // Remove duplicates (Regression #29652)
+        this.deferred[parent.id] = _.uniqBy(elements, el => el.id);
         return true;
       }
       // Otherwise, continue the chain upwards
diff --git a/spec/features/work_packages/table/hierarchy/hierarchy_parent_below_spec.rb b/spec/features/work_packages/table/hierarchy/hierarchy_parent_below_spec.rb
index 739b0023dd..8b5f0d3cb3 100644
--- a/spec/features/work_packages/table/hierarchy/hierarchy_parent_below_spec.rb
+++ b/spec/features/work_packages/table/hierarchy/hierarchy_parent_below_spec.rb
@@ -92,4 +92,53 @@ describe 'Work Package table hierarchy parent below', js: true do
       wp_table.expect_work_package_order(child.id, grandparent.id)
     end
   end
+
+  describe 'grand-parent of 2+ children visible anywhere on the page, but parent is not (Regression #29652)' do
+    let(:child) { FactoryBot.create(:work_package, subject: 'AA Child WP', project: project, type: type_task) }
+    let(:child2) { FactoryBot.create(:work_package, subject: 'BB Child WP', project: project, type: type_task) }
+    let(:parent) { FactoryBot.create(:work_package, subject: 'ZZ Parent WP', project: project, type: type_task) }
+    let(:grandparent) { FactoryBot.create(:work_package, subject: 'Grandparent', project: project, type: type_task) }
+
+    let(:query) do
+      query              = FactoryBot.build(:query, user: user, project: project)
+      query.column_names = %w(id subject)
+      query.sort_criteria = [%w(subject asc)]
+      query.show_hierarchies = true
+
+      query.save!
+      query
+    end
+
+    before do
+      child
+      parent
+      grandparent
+
+      child.update(parent_id: parent.id)
+      child2.update(parent_id: parent.id)
+      parent.update(parent_id: grandparent.id)
+
+      allow(Setting).to receive(:per_page_options).and_return '3'
+      query
+    end
+
+    it 'shows hierarchy correctly' do
+      wp_table.visit_query query
+
+      wp_table.expect_work_package_listed(child, child2, parent, grandparent)
+
+      # Expect pagination to be correct
+      expect(page).to have_selector('.pagination--item.-current', text: '3')
+
+      # Expect count to be correct (one additional parent shown)
+      expect(page).to have_selector('.wp-table--row', count: 4)
+
+      # Double order result from regression
+      wp_table.expect_work_package_order(grandparent.id, parent.id, child.id, child2.id)
+
+      # Enable hierarchy mode, should sort according to spec above
+      hierarchy.expect_hierarchy_at(grandparent, parent)
+      hierarchy.expect_leaf_at(child, child2)
+    end
+  end
 end