diff --git a/backend/app/Http/Controllers/Api/FatherRelationsController.php b/backend/app/Http/Controllers/Api/FatherRelationsController.php
index 709051dd..c3ae5931 100644
--- a/backend/app/Http/Controllers/Api/FatherRelationsController.php
+++ b/backend/app/Http/Controllers/Api/FatherRelationsController.php
@@ -10,7 +10,7 @@ use App\Models\FatherRelation;
 
 class FatherRelationsController extends Controller {
     public function register (Request $r) {
-        if (!isset($r->father_id) || !isset($r->identity)) {
+        if (!isset($r->father_id)) {
             return ['status_code' => 400, 'error_messages' => ['子の追加に失敗しました。']];
         }