diff --git a/strictdoc/git/project_diff_analyzer.py b/strictdoc/git/project_diff_analyzer.py
index 8cb1685e2..37853e574 100644
--- a/strictdoc/git/project_diff_analyzer.py
+++ b/strictdoc/git/project_diff_analyzer.py
@@ -12,6 +12,7 @@
     SDocNodeField,
 )
 from strictdoc.backend.sdoc.models.reference import (
+    ChildReqReference,
     ParentReqReference,
 )
 from strictdoc.backend.sdoc.models.section import SDocSection
@@ -134,13 +135,10 @@ def contains_requirement_relations(
         if other_requirement is None:
             return False
         for reference_ in other_requirement.relations:
-            if isinstance(reference_, ParentReqReference):
-                parent_reference: ParentReqReference = assert_cast(
-                    reference_, ParentReqReference
-                )
+            if isinstance(reference_, (ParentReqReference, ChildReqReference)):
                 if (
-                    parent_reference.ref_uid == relation_uid
-                    and parent_reference.role == relation_role
+                    reference_.ref_uid == relation_uid
+                    and reference_.role == relation_role
                 ):
                     return True
         return False
@@ -994,7 +992,9 @@ def analyze_document(
                         )
 
                 for reference_ in node.relations:
-                    if isinstance(reference_, ParentReqReference):
+                    if isinstance(
+                        reference_, (ParentReqReference, ChildReqReference)
+                    ):
                         hasher.update(reference_.ref_uid.encode("utf-8"))
                         if reference_.role is not None:
                             hasher.update(reference_.role.encode("utf-8"))
diff --git a/tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/lhs/input.sdoc b/tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/lhs/input.sdoc
similarity index 100%
rename from tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/lhs/input.sdoc
rename to tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/lhs/input.sdoc
diff --git a/tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/rhs/input.sdoc b/tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/rhs/input.sdoc
similarity index 100%
rename from tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/rhs/input.sdoc
rename to tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/rhs/input.sdoc
diff --git a/tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/strictdoc.toml b/tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/strictdoc.toml
similarity index 100%
rename from tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/strictdoc.toml
rename to tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/strictdoc.toml
diff --git a/tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/test.itest b/tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/test.itest
similarity index 100%
rename from tests/integration/features/diff/20__requirements_relations__from_requirement_to_requirement__add_parent_uid/test.itest
rename to tests/integration/features/diff/20__requirements_relations__same_document__add_parent_relation/test.itest
diff --git a/tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/lhs/input.sdoc b/tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/lhs/input.sdoc
similarity index 100%
rename from tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/lhs/input.sdoc
rename to tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/lhs/input.sdoc
diff --git a/tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/rhs/input.sdoc b/tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/rhs/input.sdoc
similarity index 100%
rename from tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/rhs/input.sdoc
rename to tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/rhs/input.sdoc
diff --git a/tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/strictdoc.toml b/tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/strictdoc.toml
similarity index 100%
rename from tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/strictdoc.toml
rename to tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/strictdoc.toml
diff --git a/tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/test.itest b/tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/test.itest
similarity index 100%
rename from tests/integration/features/diff/21__requirements_relations__from_requirement_to_requirement__remove_parent_uid/test.itest
rename to tests/integration/features/diff/21__requirements_relations__same_document__remove_parent_relation/test.itest
diff --git a/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/lhs/input1.sdoc b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/lhs/input1.sdoc
new file mode 100644
index 000000000..836dffa4d
--- /dev/null
+++ b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/lhs/input1.sdoc
@@ -0,0 +1,7 @@
+[DOCUMENT]
+TITLE: Hello world doc 1
+
+[REQUIREMENT]
+UID: REQ-1
+TITLE: Requirement #1
+STATEMENT: System shall do 1.
diff --git a/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/lhs/input2.sdoc b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/lhs/input2.sdoc
new file mode 100644
index 000000000..1d319813e
--- /dev/null
+++ b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/lhs/input2.sdoc
@@ -0,0 +1,7 @@
+[DOCUMENT]
+TITLE: Hello world doc 2
+
+[REQUIREMENT]
+UID: REQ-2
+TITLE: Requirement #2
+STATEMENT: System shall do 2.
diff --git a/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/rhs/input1.sdoc b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/rhs/input1.sdoc
new file mode 100644
index 000000000..e838362bc
--- /dev/null
+++ b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/rhs/input1.sdoc
@@ -0,0 +1,34 @@
+[DOCUMENT]
+TITLE: Hello world doc 1
+
+[GRAMMAR]
+ELEMENTS:
+- TAG: TEXT
+  FIELDS:
+  - TITLE: UID
+    TYPE: String
+    REQUIRED: False
+  - TITLE: STATEMENT
+    TYPE: String
+    REQUIRED: False
+- TAG: REQUIREMENT
+  FIELDS:
+  - TITLE: UID
+    TYPE: String
+    REQUIRED: False
+  - TITLE: TITLE
+    TYPE: String
+    REQUIRED: False
+  - TITLE: STATEMENT
+    TYPE: String
+    REQUIRED: False
+  RELATIONS:
+  - TYPE: Child
+
+[REQUIREMENT]
+UID: REQ-1
+TITLE: Requirement #1
+STATEMENT: System shall do 1.
+RELATIONS:
+- TYPE: Child
+  VALUE: REQ-2
diff --git a/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/rhs/input2.sdoc b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/rhs/input2.sdoc
new file mode 100644
index 000000000..1d319813e
--- /dev/null
+++ b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/rhs/input2.sdoc
@@ -0,0 +1,7 @@
+[DOCUMENT]
+TITLE: Hello world doc 2
+
+[REQUIREMENT]
+UID: REQ-2
+TITLE: Requirement #2
+STATEMENT: System shall do 2.
diff --git a/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/strictdoc.toml b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/strictdoc.toml
new file mode 100644
index 000000000..8da279a5a
--- /dev/null
+++ b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/strictdoc.toml
@@ -0,0 +1,6 @@
+[project]
+title = "Test Project"
+
+features = [
+  "DIFF",
+]
diff --git a/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/test.itest b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/test.itest
new file mode 100644
index 000000000..4a2f4212b
--- /dev/null
+++ b/tests/integration/features/diff/22__requirements_relations__two_docs__add_child_relation/test.itest
@@ -0,0 +1,40 @@
+RUN: %strictdoc diff %S/lhs %S/rhs --output-dir Output
+
+RUN: cat %S/Output/changelog.html | filecheck %s --check-prefix=CHECK-CHANGELOG
+
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-key">Nodes modified</div>
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-value">1</div>
+
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-key">Documents modified</div>
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-value">No documents were modified.</div>
+
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-key">Sections modified</div>
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-value">No sections were modified.</div>
+
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-key">Requirements modified</div>
+CHECK-CHANGELOG:<div class="sdoc-table_key_value-value">1 (1 modified)</div>
+
+CHECK-CHANGELOG:# 1
+CHECK-CHANGELOG:Requirement modified
+
+CHECK-CHANGELOG:REQ-1
+CHECK-CHANGELOG:Requirement #1
+CHECK-CHANGELOG:System shall do 1.
+
+CHECK-CHANGELOG:REQ-1
+CHECK-CHANGELOG:Requirement #1
+CHECK-CHANGELOG:System shall do 1.
+CHECK-CHANGELOG:text="child-relation"{{.*}}REQ-2
+CHECK-CHANGELOG:Requirement #2
+
+RUN: cat %S/Output/diff.html | filecheck %s --check-prefix=CHECK-DIFF
+
+# The left document: no specific assertions.
+CHECK-DIFF: modified="left"
+
+# The right column has REQ-1 and REQ-2 pointing to each other as child and parent.
+CHECK-DIFF: modified="right"
+CHECK-DIFF:<span class="badge" text="UID"></span><span class="sdoc_pre_content">REQ-1</span>
+CHECK-DIFF:<span class="badge" text="child-relation"></span><div class="sdoc_pre_content"><b>REQ-2</b>
+CHECK-DIFF:<span class="badge" text="UID"></span><span class="sdoc_pre_content">REQ-2</span>
+CHECK-DIFF:<span class="badge" text="relation"></span><div class="sdoc_pre_content"><b>REQ-1</b>