diff --git a/doc/api/test.md b/doc/api/test.md
index b17c3fd4f6685b..231aa956bd2a45 100644
--- a/doc/api/test.md
+++ b/doc/api/test.md
@@ -3435,6 +3435,9 @@ added:
   - v18.9.0
   - v16.19.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/63435
+    description: Added `parentId` to test events that carry a `testId`.
   - version:
     - v20.0.0
     - v19.9.0
@@ -3522,6 +3525,9 @@ Emitted when code coverage is enabled and all tests have completed.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `parentId` {number|undefined} The `testId` of the enclosing test, or
+    `undefined` for top-level tests. Lets custom reporters track lineage
+    when concurrent siblings at the same nesting level interleave.
   * `tags` {string\[]} The flattened lowercased tags declared on the test
     and its ancestor suites, in declaration order. Empty for untagged tests.
     See [Test tags][].
@@ -3548,6 +3554,9 @@ The corresponding declaration ordered events are `'test:pass'` and `'test:fail'`
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `parentId` {number|undefined} The `testId` of the enclosing test, or
+    `undefined` for top-level tests. Lets custom reporters track lineage
+    when concurrent siblings at the same nesting level interleave.
   * `tags` {string\[]} The flattened lowercased tags declared on the test
     and its ancestor suites, in declaration order. Empty for untagged tests.
     See [Test tags][].
@@ -3592,6 +3601,9 @@ defined.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `parentId` {number|undefined} The `testId` of the enclosing test, or
+    `undefined` for top-level tests. Lets custom reporters track lineage
+    when concurrent siblings at the same nesting level interleave.
   * `tags` {string\[]} The flattened lowercased tags declared on the test
     and its ancestor suites, in declaration order. Empty for untagged tests.
     See [Test tags][].
@@ -3621,6 +3633,9 @@ Emitted when a test is enqueued for execution.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `parentId` {number|undefined} The `testId` of the enclosing test, or
+    `undefined` for top-level tests. Lets custom reporters track lineage
+    when concurrent siblings at the same nesting level interleave.
   * `tags` {string\[]} The flattened lowercased tags declared on the test
     and its ancestor suites, in declaration order. Empty for untagged tests.
     See [Test tags][].
@@ -3683,6 +3698,9 @@ since the parent runner only knows about file-level tests. When using
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `parentId` {number|undefined} The `testId` of the enclosing test, or
+    `undefined` for top-level tests. Lets custom reporters track lineage
+    when concurrent siblings at the same nesting level interleave.
   * `tags` {string\[]} The flattened lowercased tags declared on the test
     and its ancestor suites, in declaration order. Empty for untagged tests.
     See [Test tags][].
@@ -3725,6 +3743,9 @@ defined.
     `undefined` if the test was run through the REPL.
   * `name` {string} The test name.
   * `nesting` {number} The nesting level of the test.
+  * `parentId` {number|undefined} The `testId` of the enclosing test, or
+    `undefined` for top-level tests. Lets custom reporters track lineage
+    when concurrent siblings at the same nesting level interleave.
   * `tags` {string\[]} The flattened lowercased tags declared on the test
     and its ancestor suites, in declaration order. Empty for untagged tests.
     See [Test tags][].
diff --git a/lib/internal/test_runner/test.js b/lib/internal/test_runner/test.js
index eb888905798bcd..5fdd80e432dc9d 100644
--- a/lib/internal/test_runner/test.js
+++ b/lib/internal/test_runner/test.js
@@ -942,7 +942,7 @@ class Test extends AsyncResource {
       const deferred = this.dequeuePendingSubtest();
       const test = deferred.test;
       this.assignReportOrder(test);
-      test.reporter.dequeue(test.nesting, test.loc, test.name, this.reportedType, test.testId, test.tags);
+      test.reporter.dequeue(test.nesting, test.loc, test.name, this.reportedType, test.testId, this.testId, test.tags);
       await test.run();
       deferred.resolve();
     }
@@ -1199,7 +1199,8 @@ class Test extends AsyncResource {
     // it. Otherwise, return a Promise to the caller and mark the test as
     // pending for later execution.
     this.parent.unfinishedSubtests.add(this);
-    this.reporter.enqueue(this.nesting, this.loc, this.name, this.reportedType, this.testId, this.tags);
+    this.reporter.enqueue(this.nesting, this.loc, this.name, this.reportedType,
+                          this.testId, this.parent?.testId, this.tags);
     if (this.root.harness.buildPromise || !this.parent.hasConcurrency()) {
       const deferred = PromiseWithResolvers();
 
@@ -1222,7 +1223,8 @@ class Test extends AsyncResource {
     }
 
     this.parent.assignReportOrder(this);
-    this.reporter.dequeue(this.nesting, this.loc, this.name, this.reportedType, this.testId, this.tags);
+    this.reporter.dequeue(this.nesting, this.loc, this.name, this.reportedType,
+                          this.testId, this.parent?.testId, this.tags);
     return this.run();
   }
 
@@ -1496,7 +1498,7 @@ class Test extends AsyncResource {
         this.testNumber ||= ++this.parent.outputSubtestCount;
         this.reporter.complete(
           this.nesting, this.loc, this.testNumber, this.name,
-          report.details, report.directive, this.testId, this.tags,
+          report.details, report.directive, this.testId, this.parent?.testId, this.tags,
         );
         this.parent.activeSubtests--;
       }
@@ -1652,12 +1654,12 @@ class Test extends AsyncResource {
     if (this.passed) {
       this.reporter.ok(
         this.nesting, this.loc, this.testNumber, this.name,
-        report.details, report.directive, this.testId, this.tags,
+        report.details, report.directive, this.testId, this.parent?.testId, this.tags,
       );
     } else {
       this.reporter.fail(
         this.nesting, this.loc, this.testNumber, this.name,
-        report.details, report.directive, this.testId, this.tags,
+        report.details, report.directive, this.testId, this.parent?.testId, this.tags,
       );
     }
 
@@ -1672,7 +1674,7 @@ class Test extends AsyncResource {
     }
     this.#reportedSubtest = true;
     this.parent.reportStarted();
-    this.reporter.start(this.nesting, this.loc, this.name, this.testId, this.tags);
+    this.reporter.start(this.nesting, this.loc, this.name, this.testId, this.parent?.testId, this.tags);
   }
 
   clearExecutionTime() {
@@ -1734,7 +1736,7 @@ class TestHook extends Test {
         __proto__: null,
         duration_ms: this.duration(),
         error,
-      }, undefined, undefined, parent.tags);
+      }, undefined, undefined, undefined, parent.tags);
     }
   }
 }
diff --git a/lib/internal/test_runner/tests_stream.js b/lib/internal/test_runner/tests_stream.js
index 622e6372fa1d13..8be33f90dfa0f2 100644
--- a/lib/internal/test_runner/tests_stream.js
+++ b/lib/internal/test_runner/tests_stream.js
@@ -35,13 +35,14 @@ class TestsStream extends Readable {
     }
   }
 
-  fail(nesting, loc, testNumber, name, details, directive, testId, tags) {
+  fail(nesting, loc, testNumber, name, details, directive, testId, parentId, tags) {
     this[kEmitMessage]('test:fail', {
       __proto__: null,
       name,
       nesting,
       testNumber,
       testId,
+      parentId,
       details,
       tags: ArrayPrototypeSlice(tags),
       ...loc,
@@ -49,13 +50,14 @@ class TestsStream extends Readable {
     });
   }
 
-  ok(nesting, loc, testNumber, name, details, directive, testId, tags) {
+  ok(nesting, loc, testNumber, name, details, directive, testId, parentId, tags) {
     this[kEmitMessage]('test:pass', {
       __proto__: null,
       name,
       nesting,
       testNumber,
       testId,
+      parentId,
       details,
       tags: ArrayPrototypeSlice(tags),
       ...loc,
@@ -63,13 +65,14 @@ class TestsStream extends Readable {
     });
   }
 
-  complete(nesting, loc, testNumber, name, details, directive, testId, tags) {
+  complete(nesting, loc, testNumber, name, details, directive, testId, parentId, tags) {
     this[kEmitMessage]('test:complete', {
       __proto__: null,
       name,
       nesting,
       testNumber,
       testId,
+      parentId,
       details,
       tags: ArrayPrototypeSlice(tags),
       ...loc,
@@ -98,36 +101,39 @@ class TestsStream extends Readable {
     return { __proto__: null, expectFailure: expectation ?? true };
   }
 
-  enqueue(nesting, loc, name, type, testId, tags) {
+  enqueue(nesting, loc, name, type, testId, parentId, tags) {
     this[kEmitMessage]('test:enqueue', {
       __proto__: null,
       nesting,
       name,
       type,
       testId,
+      parentId,
       tags: ArrayPrototypeSlice(tags),
       ...loc,
     });
   }
 
-  dequeue(nesting, loc, name, type, testId, tags) {
+  dequeue(nesting, loc, name, type, testId, parentId, tags) {
     this[kEmitMessage]('test:dequeue', {
       __proto__: null,
       nesting,
       name,
       type,
       testId,
+      parentId,
       tags: ArrayPrototypeSlice(tags),
       ...loc,
     });
   }
 
-  start(nesting, loc, name, testId, tags) {
+  start(nesting, loc, name, testId, parentId, tags) {
     this[kEmitMessage]('test:start', {
       __proto__: null,
       nesting,
       name,
       testId,
+      parentId,
       tags: ArrayPrototypeSlice(tags),
       ...loc,
     });