diff --git a/app/User.php b/app/User.php
index 1409f07..4134be2 100644
--- a/app/User.php
+++ b/app/User.php
@@ -113,7 +113,7 @@ class User extends Authenticatable
 
     public function addWife(User $wife)
     {
-        if ($this->gender_id == 1) {
+        if ($this->gender_id == 1 && ! $this->hasBeenMarriedTo($wife)) {
             $this->wifes()->save($wife);
             return $wife;
         }
@@ -128,7 +128,7 @@ class User extends Authenticatable
 
     public function addHusband(User $husband)
     {
-        if ($this->gender_id == 2) {
+        if ($this->gender_id == 2 && ! $this->hasBeenMarriedTo($husband)) {
             $this->husbands()->save($husband);
             return $husband;
         }
@@ -136,6 +136,11 @@ class User extends Authenticatable
         return false;
     }
 
+    public function hasBeenMarriedTo(User $user)
+    {
+        return $this->marriages->contains($user);
+    }
+
     public function marriages()
     {
         if ($this->gender_id == 1)
diff --git a/database/migrations/2017_06_27_151536_create_couples_table.php b/database/migrations/2017_06_27_151536_create_couples_table.php
index 76e1341..9668189 100644
--- a/database/migrations/2017_06_27_151536_create_couples_table.php
+++ b/database/migrations/2017_06_27_151536_create_couples_table.php
@@ -20,6 +20,8 @@ class CreateCouplesTable extends Migration
             $table->date('marriege_date')->nullable();
             $table->date('divorce_date')->nullable();
             $table->timestamps();
+
+            $table->unique(['husband_id', 'wife_id']);
         });
     }
 
diff --git a/tests/Feature/ManageUserFamiliesTest.php b/tests/Feature/ManageUserFamiliesTest.php
index a68af5f..22ca06f 100644
--- a/tests/Feature/ManageUserFamiliesTest.php
+++ b/tests/Feature/ManageUserFamiliesTest.php
@@ -89,7 +89,7 @@ class ManageUserFamiliesTest extends TestCase
         $wife = factory(User::class)->states('female')->create();
         $husband->addWife($wife);
 
-        $marriageId = $husband->wifes->first()->pivot->id;
+        $marriageId = $husband->fresh()->wifes->first()->pivot->id;
         $this->actingAs($husband);
 
         $this->visit(route('profile'));
@@ -265,7 +265,7 @@ class ManageUserFamiliesTest extends TestCase
         $wife = factory(User::class)->states('female')->create();
         $husband->addWife($wife);
 
-        $marriageId = $husband->wifes->first()->pivot->id;
+        $marriageId = $husband->fresh()->wifes->first()->pivot->id;
 
         $this->visit(route('profile'));
         $this->click('Set Orang Tua');
diff --git a/tests/Unit/UserTest.php b/tests/Unit/UserTest.php
index b2b19d7..defd3e7 100644
--- a/tests/Unit/UserTest.php
+++ b/tests/Unit/UserTest.php
@@ -24,12 +24,24 @@ class UserTest extends TestCase
         $wife = factory(User::class)->states('female')->create();
         $husband->addWife($wife);
 
+        $husband = $husband->fresh();
         $this->assertCount(1, $husband->wifes);
         $this->assertCount(1, $wife->husbands);
         $this->assertCount(1, $husband->marriages);
     }
 
     /** @test */
+    public function user_can_ony_marry_same_person_once()
+    {
+        $husband = factory(User::class)->states('male')->create();
+        $wife = factory(User::class)->states('female')->create();
+
+        $husband->addWife($wife);
+
+        $this->assertFalse($wife->addHusband($husband), 'This couple is married!');
+    }
+
+    /** @test */
     public function user_have_father_link_method()
     {
         $father = factory(User::class)->create();