diff --git a/backend/src/main/java/org/raddatz/familienarchiv/person/relationship/RelationshipService.java b/backend/src/main/java/org/raddatz/familienarchiv/person/relationship/RelationshipService.java
index 032c1263..d813b8e8 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/person/relationship/RelationshipService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/person/relationship/RelationshipService.java
@@ -31,6 +31,12 @@ import java.util.UUID;
 @RequiredArgsConstructor
 public class RelationshipService {
 
+    // Single source of truth for which relationship types are part of the family graph.
+    // Consulted by addRelationship (to set family_member on both endpoints) and by
+    // getFamilyNetwork (to filter the edges returned). FRIEND/COLLEAGUE/etc. are excluded.
+    private static final List<RelationType> FAMILY_RELATION_TYPES =
+            List.of(RelationType.PARENT_OF, RelationType.SPOUSE_OF, RelationType.SIBLING_OF);
+
     private final PersonRelationshipRepository relationshipRepository;
     private final PersonService personService;
     private final RelationshipInferenceService inferenceService;
@@ -64,7 +70,7 @@ public class RelationshipService {
         }
 
         List<PersonRelationship> familyEdges = relationshipRepository.findAllByRelationTypeIn(
-                List.of(RelationType.PARENT_OF, RelationType.SPOUSE_OF, RelationType.SIBLING_OF));
+                FAMILY_RELATION_TYPES);
 
         List<RelationshipDTO> edges = new ArrayList<>();
         for (PersonRelationship r : familyEdges) {
@@ -105,15 +111,23 @@ public class RelationshipService {
                 .notes(blankToNull(dto.notes()))
                 .build();
 
+        PersonRelationship saved;
         try {
             // saveAndFlush so the unique_rel constraint violates synchronously and is
             // caught here, not at commit time outside the @Transactional boundary.
-            return toDTO(relationshipRepository.saveAndFlush(rel));
+            saved = relationshipRepository.saveAndFlush(rel);
         } catch (DataIntegrityViolationException e) {
             throw DomainException.conflict(
                     ErrorCode.DUPLICATE_RELATIONSHIP,
                     "Relationship already exists for (" + personId + ", " + relatedPerson.getId() + ", " + dto.relationType() + ")");
         }
+        // Family-graph edges imply both endpoints are family members. Idempotent: the
+        // setter is a no-op when the person is already flagged, so re-imports stay clean.
+        if (FAMILY_RELATION_TYPES.contains(dto.relationType())) {
+            personService.setFamilyMember(person.getId(), true);
+            personService.setFamilyMember(relatedPerson.getId(), true);
+        }
+        return toDTO(saved);
     }
 
     @Transactional
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/person/relationship/RelationshipServiceTest.java b/backend/src/test/java/org/raddatz/familienarchiv/person/relationship/RelationshipServiceTest.java
index 0a0b963c..c8d1faf6 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/person/relationship/RelationshipServiceTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/person/relationship/RelationshipServiceTest.java
@@ -23,6 +23,8 @@ import java.util.UUID;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyBoolean;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -148,6 +150,50 @@ class RelationshipServiceTest {
         assertThat(result.notes()).isEqualTo("first born");
     }
 
+    @Test
+    void addRelationship_marks_both_endpoints_as_family_member_when_type_is_family() {
+        // Creating a family-graph edge (PARENT_OF / SPOUSE_OF / SIBLING_OF) must mark both
+        // endpoints as family members so they appear in findAllFamilyMembers and the network.
+        // This is what makes the canonical importer's relationships actually show up in the UI.
+        when(personService.getById(alice.getId())).thenReturn(alice);
+        when(personService.getById(bob.getId())).thenReturn(bob);
+        when(relationshipRepository.existsByPersonIdAndRelatedPersonIdAndRelationType(
+                bob.getId(), alice.getId(), RelationType.PARENT_OF)).thenReturn(false);
+        when(relationshipRepository.saveAndFlush(any())).thenAnswer(inv -> {
+            PersonRelationship r = inv.getArgument(0);
+            r.setId(UUID.randomUUID());
+            r.setCreatedAt(Instant.now());
+            return r;
+        });
+
+        var dto = new CreateRelationshipRequest(bob.getId(), RelationType.PARENT_OF, null, null, null);
+        service.addRelationship(alice.getId(), dto);
+
+        verify(personService).setFamilyMember(alice.getId(), true);
+        verify(personService).setFamilyMember(bob.getId(), true);
+    }
+
+    @Test
+    void addRelationship_does_not_flip_family_member_for_non_family_type() {
+        // FRIEND / COLLEAGUE / EMPLOYER / DOCTOR / NEIGHBOR / OTHER are NOT family-graph
+        // edges (see getFamilyNetwork's filter), so addRelationship must leave family_member
+        // alone — a doctor of the family is not a family member.
+        when(personService.getById(alice.getId())).thenReturn(alice);
+        when(personService.getById(bob.getId())).thenReturn(bob);
+        when(relationshipRepository.saveAndFlush(any())).thenAnswer(inv -> {
+            PersonRelationship r = inv.getArgument(0);
+            r.setId(UUID.randomUUID());
+            r.setCreatedAt(Instant.now());
+            return r;
+        });
+
+        var dto = new CreateRelationshipRequest(bob.getId(), RelationType.FRIEND, null, null, null);
+        service.addRelationship(alice.getId(), dto);
+
+        verify(personService, never()).setFamilyMember(eq(alice.getId()), anyBoolean());
+        verify(personService, never()).setFamilyMember(eq(bob.getId()), anyBoolean());
+    }
+
     @Test
     void deleteRelationship_succeeds_when_viewpoint_is_object() {
         UUID relId = UUID.randomUUID();