diff --git a/src/parent_child/qc.py b/src/parent_child/qc.py
index b0407c1..8caf8a3 100644
--- a/src/parent_child/qc.py
+++ b/src/parent_child/qc.py
@@ -2109,8 +2109,9 @@ class ParentChildEngine:
         orphan_mask = (~pm) & (~cm)
 
         if orphan_mask.any():
-            tmp = df.loc[orphan_mask, ["input_row_order"]].copy()
-            tmp = tmp.sort_values(["input_row_order"], kind="mergesort")
+            tmp = df.loc[orphan_mask, ["eff_date", "input_row_order"]].copy()
+            tmp["eff_sort"] = tmp["eff_date"].fillna(pd.Timestamp.max)
+            tmp = tmp.sort_values(["eff_sort", "input_row_order"], kind="mergesort")
             seq = pd.Series(np.arange(1, len(tmp) + 1, dtype=np.int32), index=tmp.index)
             if "AARETE_DERIVED_AMENDMENT_NUM" in df.columns:
                 amendment_str = df.loc[tmp.index, "AARETE_DERIVED_AMENDMENT_NUM"].apply(
diff --git a/src/tests/test_parent_child.py b/src/tests/test_parent_child.py
index 59ebaa3..0e1527f 100644
--- a/src/tests/test_parent_child.py
+++ b/src/tests/test_parent_child.py
@@ -1006,5 +1006,72 @@ class TestComputeRanksWithAmendmentNum(unittest.TestCase):
         self.assertEqual(result.at[3, "orphan_rank_dest"], "0.2.1")  # B=2
 
 
+class TestNormalizeAmendmentVal(unittest.TestCase):
+    """Unit tests for ParentChildEngine._normalize_amendment_val."""
+
+    def test_numeric_int(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(3), "3")
+
+    def test_numeric_float(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(3.0), "3")
+
+    def test_numeric_string(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("5"), "5")
+
+    def test_numeric_float_string(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("7.0"), "7")
+
+    def test_letter_A_upper(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("A"), "1")
+
+    def test_letter_B_upper(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("B"), "2")
+
+    def test_letter_C_upper(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("C"), "3")
+
+    def test_letter_F_upper(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("F"), "6")
+
+    def test_letter_Z_upper(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("Z"), "26")
+
+    def test_letter_a_lower(self):
+        """Lowercase letters are also converted (a=1)."""
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("a"), "1")
+
+    def test_letter_b_lower(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("b"), "2")
+
+    def test_letter_f_lower(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("f"), "6")
+
+    def test_nan_returns_zero(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(np.nan), "0")
+
+    def test_none_returns_zero(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(None), "0")
+
+    def test_empty_string_returns_zero(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(""), "0")
+
+    def test_whitespace_only_returns_zero(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("   "), "0")
+
+    def test_multi_char_string_returned_as_is(self):
+        """Multi-character non-numeric strings are returned as-is."""
+        self.assertEqual(ParentChildEngine._normalize_amendment_val("AB"), "AB")
+
+    def test_letter_with_whitespace(self):
+        """Letter with surrounding whitespace is still converted."""
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(" A "), "1")
+
+    def test_zero_value(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(0), "0")
+
+    def test_negative_number(self):
+        self.assertEqual(ParentChildEngine._normalize_amendment_val(-1), "-1")
+
+
 if __name__ == "__main__":
     unittest.main()