diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5ea16e7fc..6a3d24a1d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,10 +11,8 @@ and this project adheres to
 ## Unreleased
 
 <!-- write down unreleased development here -->
+* [person] prevent duplicate relationship in filiation/household graph (https://gitlab.com/champs-libres/departement-de-la-vendee/chill/-/issues/560)
 * [Documents] Validate storedObject and allow for null data (https://gitlab.com/champs-libres/departement-de-la-vendee/chill/-/issues/565)
-* [Activity form] invert 'incoming' and 'receiving' in Activity form
-* [Activity form] keep the same order for 'attendee' field in new and edit form
-* [list with period] use "sameas" test operator to introduce requestor in list
 
 ## Test releases
 
diff --git a/src/Bundle/ChillPersonBundle/Entity/Relationships/Relationship.php b/src/Bundle/ChillPersonBundle/Entity/Relationships/Relationship.php
index d51881bb2..62fbb63a9 100644
--- a/src/Bundle/ChillPersonBundle/Entity/Relationships/Relationship.php
+++ b/src/Bundle/ChillPersonBundle/Entity/Relationships/Relationship.php
@@ -15,6 +15,7 @@ use Chill\MainBundle\Doctrine\Model\TrackCreationInterface;
 use Chill\MainBundle\Doctrine\Model\TrackUpdateInterface;
 use Chill\MainBundle\Entity\User;
 use Chill\PersonBundle\Entity\Person;
+use Chill\PersonBundle\Validator\Constraints\Relationship\RelationshipNoDuplicate;
 use DateTimeImmutable;
 use DateTimeInterface;
 use Doctrine\ORM\Mapping as ORM;
@@ -31,6 +32,7 @@ use Symfony\Component\Validator\Constraints as Assert;
  * @DiscriminatorMap(typeProperty="type", mapping={
  *     "relationship": Relationship::class
  * })
+ * @RelationshipNoDuplicate
  */
 class Relationship implements TrackCreationInterface, TrackUpdateInterface
 {
diff --git a/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/App.vue b/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/App.vue
index f5db187b9..f86c68576 100644
--- a/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/App.vue
+++ b/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/App.vue
@@ -472,15 +472,25 @@ export default {
 
             case 'create':
                return postRelationship(this.modal.data)
-               .then(relationship => new Promise(resolve => {
-                  //console.log('post relationship response', relationship)
-                  this.$store.dispatch('addLinkFromRelationship', relationship)
-                  this.modal.showModal = false
-                  this.resetForm()
-                  this.forceUpdateComponent()
-                  resolve()
-               }))
-               .catch()
+                  .then(relationship => new Promise(resolve => {
+                     //console.log('post relationship response', relationship)
+                     this.$store.dispatch('addLinkFromRelationship', relationship)
+                     this.modal.showModal = false
+                     this.resetForm()
+                     this.forceUpdateComponent()
+                     resolve()
+                  }))
+                  .catch( error => {
+                     if (error.name === 'ValidationException') {
+                        for (let v of error.violations) {
+                           this.$toast.open({message: v });
+                           console.log(v)
+                        }
+                     } else {
+                        this.$toast.open({message: 'An error occurred'});
+                     }
+                  }
+               )
 
             case 'edit':
                return patchRelationship(this.modal.data)
diff --git a/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/api.js b/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/api.js
index 448ff6633..01c335436 100644
--- a/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/api.js
+++ b/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/api.js
@@ -1,50 +1,5 @@
-import { splitId } from './vis-network'
-
-/**
- * @function makeFetch
- * @param method
- * @param url
- * @param body
- * @returns {Promise<Response>}
- */
-const makeFetch = (method, url, body) => {
-    return fetch(url, {
-        method: method,
-        headers: {
-            'Content-Type': 'application/json;charset=utf-8'
-        },
-        body: (body !== null) ? JSON.stringify(body) : null
-    })
-    .then(response => {
-
-        if (response.ok) {
-            return response.json();
-        }
-
-        if (response.status === 422) {
-            return response.json().then(violations => {
-                throw ValidationException(violations)
-            });
-        }
-
-        throw {
-            msg: 'Error while updating AccompanyingPeriod Course.',
-            sta: response.status,
-            txt: response.statusText,
-            err: new Error(),
-            body: response.body
-        };
-    });
-}
-
-/**
- * @param violations
- * @constructor
- */
-const ValidationException = (violations) => {
-    this.violations = violations
-    this.name = 'ValidationException'
-}
+import { splitId } from './vis-network';
+import {makeFetch} from 'ChillMainAssets/lib/api/apiMethods.js';
 
 /**
  * @function getFetch
@@ -136,7 +91,7 @@ const getRelationsList = () => {
  * @returns {Promise<Response>}
  */
 const postRelationship = (relationship) => {
-    //console.log(relationship)
+    //console.log(relationship);
     return postFetch(
         `/api/1.0/relations/relationship.json`,
         {
diff --git a/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/index.js b/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/index.js
index 5e8989e49..a64afd4a1 100644
--- a/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/index.js
+++ b/src/Bundle/ChillPersonBundle/Resources/public/vuejs/VisGraph/index.js
@@ -3,8 +3,10 @@ import { store } from "./store.js"
 import { _createI18n } from 'ChillMainAssets/vuejs/_js/i18n'
 import { visMessages } from './i18n'
 import App from './App.vue'
+import VueToast from 'vue-toast-notification';
+import 'vue-toast-notification/dist/theme-sugar.css';
 
-import './vis-network'
+import './vis-network';
 
 const i18n = _createI18n(visMessages)
 const container = document.getElementById('relationship-graph')
@@ -25,5 +27,11 @@ const app = createApp({
 })
 .use(store)
 .use(i18n)
+.use(VueToast, {
+    position: "bottom-right",
+    type: "error",
+    duration: 5000,
+    dismissible: true
+ })
 .component('app', App)
 .mount('#relationship-graph')
diff --git a/src/Bundle/ChillPersonBundle/Validator/Constraints/Relationship/RelationshipNoDuplicate.php b/src/Bundle/ChillPersonBundle/Validator/Constraints/Relationship/RelationshipNoDuplicate.php
new file mode 100644
index 000000000..db4d7c0d6
--- /dev/null
+++ b/src/Bundle/ChillPersonBundle/Validator/Constraints/Relationship/RelationshipNoDuplicate.php
@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Chill\PersonBundle\Validator\Constraints\Relationship;
+
+use Symfony\Component\Validator\Constraint;
+
+/**
+ * @Annotation
+ */
+class RelationshipNoDuplicate extends Constraint
+{
+    public $message = 'relationship.duplicate';
+
+    public function getTargets()
+    {
+        return self::CLASS_CONSTRAINT;
+    }
+}
diff --git a/src/Bundle/ChillPersonBundle/Validator/Constraints/Relationship/RelationshipNoDuplicateValidator.php b/src/Bundle/ChillPersonBundle/Validator/Constraints/Relationship/RelationshipNoDuplicateValidator.php
new file mode 100644
index 000000000..580fc4b48
--- /dev/null
+++ b/src/Bundle/ChillPersonBundle/Validator/Constraints/Relationship/RelationshipNoDuplicateValidator.php
@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Chill\PersonBundle\Validator\Constraints\Relationship;
+
+use Chill\PersonBundle\Repository\Relationships\RelationshipRepository;
+use Symfony\Component\Form\Exception\UnexpectedTypeException;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+class RelationshipNoDuplicateValidator extends ConstraintValidator
+{
+    private RelationshipRepository $relationshipRepository;
+
+    public function __construct(RelationshipRepository $relationshipRepository)
+    {
+        $this->relationshipRepository = $relationshipRepository;
+    }
+
+    public function validate($relationship, Constraint $constraint)
+    {
+        if (!$constraint instanceof RelationshipNoDuplicate) {
+            throw new UnexpectedTypeException($constraint, RelationshipNoDuplicate::class);
+        }
+
+        $fromPerson = $relationship->getFromPerson();
+        $toPerson = $relationship->getToPerson();
+
+        $relationships = $this->relationshipRepository->findBy([
+            'fromPerson' => [$fromPerson, $toPerson],
+            'toPerson' => [$fromPerson, $toPerson],
+        ]);
+
+        foreach ($relationships as $r) {
+            if (
+                $r->getFromPerson() === $fromPerson
+                || $r->getFromPerson() === $toPerson
+                || $r->getToPerson() === $fromPerson
+                || $r->getToPerson() === $toPerson
+            ) {
+                $this->context->buildViolation($constraint->message)
+                    ->addViolation();
+            }
+        }
+    }
+}
diff --git a/src/Bundle/ChillPersonBundle/migrations/Version20220425000000.php b/src/Bundle/ChillPersonBundle/migrations/Version20220425000000.php
new file mode 100644
index 000000000..1dd50d224
--- /dev/null
+++ b/src/Bundle/ChillPersonBundle/migrations/Version20220425000000.php
@@ -0,0 +1,36 @@
+<?php
+
+/**
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Chill\Migrations\Person;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Add constraint with a index on chill_person_relationships.
+ */
+final class Version20220425000000 extends AbstractMigration
+{
+    public function down(Schema $schema): void
+    {
+        $this->addSql('DROP INDEX IDX_RELATIONSHIPS000');
+    }
+
+    public function getDescription(): string
+    {
+        return 'Add constraint with a index on chill_person_relationships.';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('CREATE UNIQUE INDEX IDX_RELATIONSHIPS000 ON chill_person_relationships (least(fromperson_id, toperson_id), greatest(fromperson_id, toperson_id))');
+    }
+}
diff --git a/src/Bundle/ChillPersonBundle/translations/validators.fr.yml b/src/Bundle/ChillPersonBundle/translations/validators.fr.yml
index 13fcb54fb..b2bc549d7 100644
--- a/src/Bundle/ChillPersonBundle/translations/validators.fr.yml
+++ b/src/Bundle/ChillPersonBundle/translations/validators.fr.yml
@@ -62,3 +62,7 @@ You cannot associate a resource with the same person: Vous ne pouvez pas ajouter
 #location
 The period must remain located: 'Un parcours doit être localisé'
 The person where the course is located must be associated to the course. Change course's location before removing the person.: "Le parcours est localisé auprès cet usager. Veuillez changer la localisation du parcours avant de suprimer l'usager"
+
+#relationship
+relationship:
+    duplicate: Une relation de filiation existe déjà entre ces 2 personnes
\ No newline at end of file