diff --git a/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonRegisterImporter.java b/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonRegisterImporter.java
index 1058938b..490694c5 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonRegisterImporter.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonRegisterImporter.java
@@ -2,6 +2,7 @@ package org.raddatz.familienarchiv.importing;
 
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
+import org.raddatz.familienarchiv.person.PersonGeneration;
 import org.raddatz.familienarchiv.person.PersonService;
 import org.raddatz.familienarchiv.person.PersonType;
 import org.raddatz.familienarchiv.person.PersonUpsertCommand;
@@ -33,8 +34,6 @@ public class PersonRegisterImporter {
     // carry an inline note. Out-of-range values are caught by the post-parse
     // range guard, not by the regex.
     private static final Pattern GENERATION_PATTERN = Pattern.compile("^\\s*G?\\s*(-?\\d+)");
-    private static final int GENERATION_MIN = 0;
-    private static final int GENERATION_MAX = 10;
 
     private final PersonService personService;
 
@@ -68,16 +67,16 @@ public class PersonRegisterImporter {
 
     /**
      * Parses an optional {@code G n} generation cell. Returns null for blanks,
-     * non-matching strings, and any value outside {@value #GENERATION_MIN}..{@value #GENERATION_MAX}
-     * (mirroring the V70 CHECK). Out-of-range values log a WARN but never abort
-     * the batch — REQ-IMP-001.
+     * non-matching strings, and any value outside the {@link PersonGeneration}
+     * bounds (mirroring the V70 CHECK). Out-of-range values log a WARN but
+     * never abort the batch — REQ-IMP-001.
      */
     static Integer parseGeneration(String raw, String personId) {
         if (raw == null || raw.isBlank()) return null;
         Matcher m = GENERATION_PATTERN.matcher(raw);
         if (!m.find()) return null;
         int parsed = Integer.parseInt(m.group(1));
-        if (parsed < GENERATION_MIN || parsed > GENERATION_MAX) {
+        if (parsed < PersonGeneration.MIN_GENERATION || parsed > PersonGeneration.MAX_GENERATION) {
             log.warn("Skipping out-of-range generation '{}' for row {}", raw, personId);
             return null;
         }
diff --git a/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java b/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java
index 56eab828..df402050 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/importing/PersonTreeImporter.java
@@ -7,6 +7,7 @@ import lombok.extern.slf4j.Slf4j;
 import org.raddatz.familienarchiv.exception.DomainException;
 import org.raddatz.familienarchiv.exception.ErrorCode;
 import org.raddatz.familienarchiv.person.Person;
+import org.raddatz.familienarchiv.person.PersonGeneration;
 import org.raddatz.familienarchiv.person.PersonService;
 import org.raddatz.familienarchiv.person.PersonType;
 import org.raddatz.familienarchiv.person.PersonUpsertCommand;
@@ -87,24 +88,21 @@ public class PersonTreeImporter {
     }
 
     /**
-     * Returns the JSON {@code generation} value if present and in
-     * {@value #GENERATION_MIN}..{@value #GENERATION_MAX}; null otherwise. Out-of-range
-     * values log a WARN but never abort the batch — mirrors the register-importer
+     * Returns the JSON {@code generation} value if present and within the
+     * {@link PersonGeneration} bounds; null otherwise. Out-of-range values
+     * log a WARN but never abort the batch — mirrors the register-importer
      * skip-and-warn policy.
      */
     private static Integer generationOrNull(JsonNode node, String personId) {
         Integer raw = intOrNull(node, "generation");
         if (raw == null) return null;
-        if (raw < GENERATION_MIN || raw > GENERATION_MAX) {
+        if (raw < PersonGeneration.MIN_GENERATION || raw > PersonGeneration.MAX_GENERATION) {
             log.warn("Skipping out-of-range generation '{}' for person {}", raw, personId);
             return null;
         }
         return raw;
     }
 
-    private static final int GENERATION_MIN = 0;
-    private static final int GENERATION_MAX = 10;
-
     private int createRelationships(JsonNode relationships, Map<String, UUID> idByRowId) {
         int created = 0;
         for (JsonNode node : relationships) {
diff --git a/backend/src/main/java/org/raddatz/familienarchiv/person/PersonGeneration.java b/backend/src/main/java/org/raddatz/familienarchiv/person/PersonGeneration.java
new file mode 100644
index 00000000..cea036cd
--- /dev/null
+++ b/backend/src/main/java/org/raddatz/familienarchiv/person/PersonGeneration.java
@@ -0,0 +1,16 @@
+package org.raddatz.familienarchiv.person;
+
+/**
+ * Single source of truth for the {@code persons.generation} value range.
+ * The DB CHECK in V70, the {@code PersonUpdateDTO} Bean Validation annotations,
+ * and the canonical importers all reference these constants so a future widening
+ * (e.g. accepting {@code G −1} ancestors) happens in one place. Mirror this file
+ * by hand in the V70 migration comment when adjusting bounds.
+ */
+public final class PersonGeneration {
+
+    public static final int MIN_GENERATION = 0;
+    public static final int MAX_GENERATION = 10;
+
+    private PersonGeneration() {}
+}
diff --git a/backend/src/main/java/org/raddatz/familienarchiv/person/PersonUpdateDTO.java b/backend/src/main/java/org/raddatz/familienarchiv/person/PersonUpdateDTO.java
index a462943c..a3cd9aca 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/person/PersonUpdateDTO.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/person/PersonUpdateDTO.java
@@ -23,9 +23,9 @@ public class PersonUpdateDTO {
     private String notes;
     private Integer birthYear;
     private Integer deathYear;
-    // Mirror of the persons.generation CHECK constraint (V70).
-    // null clears the field; 0..10 is the allowlist of valid indices.
-    @Min(0)
-    @Max(10)
+    // Mirror of the persons.generation CHECK constraint (V70). Bounds live in
+    // PersonGeneration so DB, DTO, and importer all read from one place.
+    @Min(PersonGeneration.MIN_GENERATION)
+    @Max(PersonGeneration.MAX_GENERATION)
     private Integer generation;
 }
diff --git a/backend/src/main/resources/db/migration/V70__add_generation_to_persons.sql b/backend/src/main/resources/db/migration/V70__add_generation_to_persons.sql
index acb39b30..5693720b 100644
--- a/backend/src/main/resources/db/migration/V70__add_generation_to_persons.sql
+++ b/backend/src/main/resources/db/migration/V70__add_generation_to_persons.sql
@@ -10,11 +10,13 @@
 
 ALTER TABLE persons ADD COLUMN generation SMALLINT;
 
--- Allowlist of valid generation indices. The upper bound is intentionally
--- loose — current data tops out at G 5, but a future G 6 → G 10 widening
--- needs no migration. A G −1 ancestor would require a separate one-shot
--- shift migration (out of scope here; the layout's normalise step already
--- handles negative seeds at render time).
+-- Allowlist of valid generation indices. The 0..10 bounds mirror
+-- PersonGeneration.MIN_GENERATION / MAX_GENERATION in Java — keep the
+-- two in sync (the DTO @Min/@Max and both importer range guards read from
+-- those Java constants). Current data tops out at G 5, but a future G 6 →
+-- G 10 widening needs no migration. A G −1 ancestor would require a
+-- separate one-shot shift migration (out of scope here; the layout's
+-- normalise step already handles negative seeds at render time).
 ALTER TABLE persons ADD CONSTRAINT chk_generation_range
     CHECK (generation IS NULL OR generation BETWEEN 0 AND 10);