diff --git a/cylc/flow/task_pool.py b/cylc/flow/task_pool.py
index 8e8b639914..d46e7cd4ad 100644
--- a/cylc/flow/task_pool.py
+++ b/cylc/flow/task_pool.py
@@ -18,6 +18,7 @@
 
 from collections import Counter
 from contextlib import suppress
+import itertools
 import json
 import logging
 from textwrap import indent
@@ -90,6 +91,7 @@
     TASK_STATUSES_FINAL,
 )
 from cylc.flow.task_trigger import TaskTrigger
+from cylc.flow.taskdef import generate_graph_children
 from cylc.flow.util import deserialise_set
 from cylc.flow.workflow_status import StopMode
 
@@ -917,13 +919,19 @@ def _get_task_by_id(self, id_: str) -> Optional[TaskProxy]:
         return None
 
     def queue_task(self, itask: TaskProxy) -> None:
-        """Queue a task that is ready to run."""
+        """Queue a task that is ready to run.
+
+        If it is already queued, do nothing.
+        """
         if itask.state_reset(is_queued=True):
             self.data_store_mgr.delta_task_queued(itask)
             self.task_queue_mgr.push_task(itask)
 
     def unqueue_task(self, itask: TaskProxy) -> None:
-        """Un-queue a task that is no longer ready to run."""
+        """Un-queue a task that is no longer ready to run.
+
+        If it is not queued, do nothing.
+        """
         if itask.state_reset(is_queued=False):
             self.data_store_mgr.delta_task_queued(itask)
             self.task_queue_mgr.remove_task(itask)
@@ -2103,30 +2111,34 @@ def remove_tasks(
             *(quick_relative_id(cycle, task) for task, cycle in inactive),
         }
 
-        # Unset any prereqs naturally satisfied by these tasks
-        # (do not unset those satisfied by `cylc set --pre`):
-        for itask in self.get_tasks():
-            fnums_to_remove = itask.match_flows(flow_nums)
-            if not fnums_to_remove:
-                continue
-            for prereq in (
-                *itask.state.prerequisites,
-                *itask.state.suicide_prerequisites,
-            ):
-                for msg in prereq.naturally_satisfied_dependencies():
-                    id_ = msg.get_id()
-                    if id_ in matched_task_ids:
-                        prereq[msg] = False
-                        if id_ not in removed:
-                            removed[id_] = fnums_to_remove
-            if not itask.prereqs_are_satisfied():
-                self.unqueue_task(itask)
-
-        # Remove from DB tables:
         for id_ in matched_task_ids:
-            point, name = id_.split('/', 1)
+            point_str, name = id_.split('/', 1)
+            tdef = self.config.taskdefs[name]
+            # Unset any prereqs naturally satisfied by these tasks
+            # (do not unset those satisfied by `cylc set --pre`):
+            for child in itertools.chain.from_iterable(
+                generate_graph_children(tdef, get_point(point_str)).values()
+            ):
+                child_itask = self.get_task(child.point, child.name)
+                if not child_itask:
+                    continue
+                fnums_to_remove = child_itask.match_flows(flow_nums)
+                if not fnums_to_remove:
+                    continue
+                for prereq in (
+                    *child_itask.state.prerequisites,
+                    *child_itask.state.suicide_prerequisites,
+                ):
+                    for msg in prereq.naturally_satisfied_dependencies():
+                        if msg.get_id() == id_:
+                            prereq[msg] = False
+                            self.unqueue_task(child_itask)
+                            if id_ not in removed:
+                                removed[id_] = fnums_to_remove
+
+            # Remove from DB tables:
             db_removed_fnums = self.workflow_db_mgr.remove_task_from_flows(
-                point, name, flow_nums
+                point_str, name, flow_nums
             )
             if db_removed_fnums:
                 removed.setdefault(id_, set()).update(db_removed_fnums)