diff --git a/public/pages/contacts.js b/public/pages/contacts.js
index a788954..fee65f3 100644
--- a/public/pages/contacts.js
+++ b/public/pages/contacts.js
@@ -240,9 +240,11 @@ function renderContactItem(c) {
            class="contact-action-btn" aria-label="${t('contacts.exportLabel')}" title="${t('contacts.exportTooltip')}">
           <i data-lucide="download" style="width:16px;height:16px;" aria-hidden="true"></i>
         </a>
-        <button class="contact-action-btn" data-action="delete" data-id="${c.id}" aria-label="${t('contacts.deleteLabel')}">
-          <i data-lucide="trash-2" style="width:16px;height:16px;" aria-hidden="true"></i>
-        </button>
+        ${!c.family_user_id ? `
+          <button class="contact-action-btn" data-action="delete" data-id="${c.id}" aria-label="${t('contacts.deleteLabel')}">
+            <i data-lucide="trash-2" style="width:16px;height:16px;" aria-hidden="true"></i>
+          </button>
+        ` : ''}
       </div>
     </div>
   `;
@@ -288,7 +290,7 @@ function openContactModal({ mode, contact = null }) {
     </div>
 
     <div class="modal-panel__footer" style="border:none;padding:0;margin-top:var(--space-4)">
-      ${isEdit ? `<button class="btn btn--danger btn--icon" id="cm-delete" aria-label="${t('contacts.deleteLabel')}">
+      ${isEdit && !contact.family_user_id ? `<button class="btn btn--danger btn--icon" id="cm-delete" aria-label="${t('contacts.deleteLabel')}">
         <i data-lucide="trash-2" style="width:16px;height:16px;" aria-hidden="true"></i>
       </button>` : '<div></div>'}
       <div style="display:flex;gap:var(--space-3);">
diff --git a/server/routes/contacts.js b/server/routes/contacts.js
index 8d7f1b3..1eba2b3 100644
--- a/server/routes/contacts.js
+++ b/server/routes/contacts.js
@@ -138,6 +138,13 @@ router.put('/:id', (req, res) => {
 router.delete('/:id', (req, res) => {
   try {
     const id     = parseInt(req.params.id, 10);
+    const contact = db.get().prepare('SELECT family_user_id FROM contacts WHERE id = ?').get(id);
+    if (!contact) return res.status(404).json({ error: 'Kontakt nicht gefunden', code: 404 });
+    
+    if (contact.family_user_id) {
+      return res.status(403).json({ error: 'Familienmitglieder können nicht aus der Kontaktliste gelöscht werden.', code: 403 });
+    }
+
     const result = db.get().prepare('DELETE FROM contacts WHERE id = ?').run(id);
     if (result.changes === 0)
       return res.status(404).json({ error: 'Kontakt nicht gefunden', code: 404 });
diff --git a/test-family-contacts.js b/test-family-contacts.js
new file mode 100644
index 0000000..1c11ff1
--- /dev/null
+++ b/test-family-contacts.js
@@ -0,0 +1,60 @@
+import { DatabaseSync } from 'node:sqlite';
+import { MIGRATIONS_SQL } from './server/db-schema-test.js';
+
+let passed = 0, failed = 0;
+function test(name, fn) {
+  try { fn(); console.log(`  ✓ ${name}`); passed++; }
+  catch (err) { console.error(`  ✗ ${name}: ${err.message}`); failed++; }
+}
+function assert(cond, msg) { if (!cond) throw new Error(msg || 'Assertion failed'); }
+
+const db = new DatabaseSync(':memory:');
+db.exec('PRAGMA foreign_keys = ON;');
+
+// Setup schema up to migration 23 (where family_user_id was added)
+// Since we don't have all migrations in SQL strings easily available, 
+// we'll just mock the necessary tables for this specific test.
+db.exec(`
+  CREATE TABLE users (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    display_name TEXT NOT NULL
+  );
+  CREATE TABLE contacts (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT NOT NULL,
+    family_user_id INTEGER REFERENCES users(id) ON DELETE CASCADE
+  );
+`);
+
+const userId = db.prepare("INSERT INTO users (display_name) VALUES ('Papa')").run().lastInsertRowid;
+const contactIdFamily = db.prepare("INSERT INTO contacts (name, family_user_id) VALUES ('Papa', ?)").run(userId).lastInsertRowid;
+const contactIdRegular = db.prepare("INSERT INTO contacts (name, family_user_id) VALUES ('Regular Contact', NULL)").run().lastInsertRowid;
+
+console.log('\n[Family-Contacts-Test] Backend Deletion Prevention\n');
+
+test('Regular contact can be deleted', () => {
+  const result = db.prepare('DELETE FROM contacts WHERE id = ?').run(contactIdRegular);
+  assert(result.changes === 1, 'Should have deleted 1 row');
+});
+
+test('Family contact should NOT be deleted if we apply the logic from the route', () => {
+  // Mocking the logic in server/routes/contacts.js
+  const id = contactIdFamily;
+  const contact = db.prepare('SELECT family_user_id FROM contacts WHERE id = ?').get(id);
+  
+  let deleted = false;
+  let forbidden = false;
+  
+  if (contact.family_user_id) {
+    forbidden = true;
+  } else {
+    db.prepare('DELETE FROM contacts WHERE id = ?').run(id);
+    deleted = true;
+  }
+  
+  assert(forbidden === true, 'Should be forbidden');
+  assert(deleted === false, 'Should not have been deleted');
+});
+
+console.log(`\nResults: ${passed} passed, ${failed} failed\n`);
+if (failed > 0) process.exit(1);