diff --git a/docs/architecture/c4-diagrams.md b/docs/architecture/c4-diagrams.md
index 5e502d30..6467998d 100644
--- a/docs/architecture/c4-diagrams.md
+++ b/docs/architecture/c4-diagrams.md
@@ -242,6 +242,7 @@ C4Component
         Component(relInference, "RelationshipInferenceService", "Spring Service", "Computes transitive family relationships from explicit edges to infer grandparent/grandchild, aunt/uncle, and other extended-family links for the network graph.")
 
         Component(personRepo, "PersonRepository", "Spring Data JPA", "Queries persons with name search (including aliases), correspondent discovery, person summaries with document counts, and merge/reassignment helpers.")
+        Component(relRepo, "PersonRelationshipRepository", "Spring Data JPA", "Reads and writes PersonRelationship records. Supports lookup by person ID, by relation type, and existence checks for deduplication.")
     }
 
     Rel(frontend, personCtrl, "Person requests", "HTTP / JSON")
@@ -250,9 +251,10 @@ C4Component
     Rel(relCtrl, relSvc, "Delegates to", "")
     Rel(relCtrl, relInference, "Queries inferred graph", "")
     Rel(personSvc, personRepo, "Reads / writes persons", "")
-    Rel(relSvc, db, "Reads / writes relationships", "JDBC")
-    Rel(relInference, db, "Reads relationships for inference", "JDBC")
+    Rel(relSvc, relRepo, "Reads / writes relationships", "")
+    Rel(relInference, relRepo, "Reads relationships for inference", "")
     Rel(personRepo, db, "SQL queries", "JDBC")
+    Rel(relRepo, db, "SQL queries", "JDBC")
 ```
 
 ### 3d — OCR Orchestration