diff --git a/homeassistant/components/advantage_air/__init__.py b/homeassistant/components/advantage_air/__init__.py
index 4114f612fe95..7d2a5515f794 100644
--- a/homeassistant/components/advantage_air/__init__.py
+++ b/homeassistant/components/advantage_air/__init__.py
@@ -4,7 +4,7 @@ from advantage_air import advantage_air
 
 from homeassistant.const import CONF_IP_ADDRESS, CONF_PORT, Platform
 from homeassistant.core import HomeAssistant
-from homeassistant.helpers import config_validation as cv
+from homeassistant.helpers import config_validation as cv, device_registry as dr
 from homeassistant.helpers.aiohttp_client import async_get_clientsession
 from homeassistant.helpers.typing import ConfigType
 
@@ -50,6 +50,18 @@ async def async_setup_entry(
 
     entry.runtime_data = coordinator
 
+    # Register the system device so child devices can resolve it as their
+    # via_device parent regardless of platform setup order.
+    system = coordinator.data["system"]
+    dr.async_get(hass).async_get_or_create(
+        config_entry_id=entry.entry_id,
+        identifiers={(DOMAIN, system["rid"])},
+        manufacturer="Advantage Air",
+        model=system["sysType"],
+        name=system["name"],
+        sw_version=system["myAppRev"],
+    )
+
     await hass.config_entries.async_forward_entry_setups(entry, PLATFORMS)
 
     return True
diff --git a/homeassistant/components/advantage_air/entity.py b/homeassistant/components/advantage_air/entity.py
index c0f4cd5512c2..975cc901871c 100644
--- a/homeassistant/components/advantage_air/entity.py
+++ b/homeassistant/components/advantage_air/entity.py
@@ -5,6 +5,7 @@ from typing import Any
 from advantage_air import ApiError
 
 from homeassistant.exceptions import HomeAssistantError
+from homeassistant.helpers import device_registry as dr
 from homeassistant.helpers.device_registry import DeviceInfo
 from homeassistant.helpers.update_coordinator import CoordinatorEntity
 
@@ -49,7 +50,11 @@ class AdvantageAirAcEntity(AdvantageAirEntity):
         self._attr_unique_id += f"-{ac_key}"
 
         self._attr_device_info = DeviceInfo(
-            via_device=(DOMAIN, self.coordinator.data["system"]["rid"]),
+            via_device_id=dr.async_get_device_id_by_identifier(
+                self.coordinator.hass,
+                (DOMAIN, self.coordinator.data["system"]["rid"]),
+                config_entry_id=self.coordinator.config_entry.entry_id,
+            ),
             identifiers={(DOMAIN, self._attr_unique_id)},
             manufacturer="Advantage Air",
             model=self.coordinator.data["system"]["sysType"],
@@ -105,7 +110,11 @@ class AdvantageAirThingEntity(AdvantageAirEntity):
         self._attr_unique_id += f"-{self._id}"
 
         self._attr_device_info = DeviceInfo(
-            via_device=(DOMAIN, self.coordinator.data["system"]["rid"]),
+            via_device_id=dr.async_get_device_id_by_identifier(
+                self.coordinator.hass,
+                (DOMAIN, self.coordinator.data["system"]["rid"]),
+                config_entry_id=self.coordinator.config_entry.entry_id,
+            ),
             identifiers={(DOMAIN, self._attr_unique_id)},
             manufacturer="Advantage Air",
             model="MyPlace",
diff --git a/homeassistant/components/advantage_air/light.py b/homeassistant/components/advantage_air/light.py
index d3c94da3fd1a..a76f30a33e9c 100644
--- a/homeassistant/components/advantage_air/light.py
+++ b/homeassistant/components/advantage_air/light.py
@@ -4,6 +4,7 @@ from typing import Any, override
 
 from homeassistant.components.light import ATTR_BRIGHTNESS, ColorMode, LightEntity
 from homeassistant.core import HomeAssistant
+from homeassistant.helpers import device_registry as dr
 from homeassistant.helpers.device_registry import DeviceInfo
 from homeassistant.helpers.entity_platform import AddConfigEntryEntitiesCallback
 
@@ -55,7 +56,11 @@ class AdvantageAirLight(AdvantageAirEntity, LightEntity):
         self._attr_unique_id += f"-{self._id}"
         self._attr_device_info = DeviceInfo(
             identifiers={(DOMAIN, self._attr_unique_id)},
-            via_device=(DOMAIN, self.coordinator.data["system"]["rid"]),
+            via_device_id=dr.async_get_device_id_by_identifier(
+                self.coordinator.hass,
+                (DOMAIN, self.coordinator.data["system"]["rid"]),
+                config_entry_id=self.coordinator.config_entry.entry_id,
+            ),
             manufacturer="Advantage Air",
             model=light.get("moduleType"),
             name=light["name"],
diff --git a/tests/components/advantage_air/test_init.py b/tests/components/advantage_air/test_init.py
index e700485c75a1..ff5c8ebc506b 100644
--- a/tests/components/advantage_air/test_init.py
+++ b/tests/components/advantage_air/test_init.py
@@ -3,9 +3,12 @@
 from unittest.mock import AsyncMock
 
 from advantage_air import ApiError
+import pytest
 
+from homeassistant.components.advantage_air.const import DOMAIN
 from homeassistant.config_entries import ConfigEntryState
 from homeassistant.core import HomeAssistant
+from homeassistant.helpers import device_registry as dr
 
 from . import add_mock_config, patch_get
 
@@ -21,6 +24,36 @@ async def test_async_setup_entry(hass: HomeAssistant, mock_get: AsyncMock) -> No
     assert entry.state is ConfigEntryState.NOT_LOADED
 
 
+@pytest.mark.usefixtures("mock_get")
+@pytest.mark.parametrize(
+    "child_identifier",
+    [
+        "uniqueid-ac1",  # AC device
+        "uniqueid-100",  # myLights light device
+        "uniqueid-203",  # myThings device
+    ],
+)
+async def test_child_devices_via_device(
+    hass: HomeAssistant,
+    device_registry: dr.DeviceRegistry,
+    child_identifier: str,
+) -> None:
+    """Test child devices link to the system device via via_device_id."""
+
+    entry = await add_mock_config(hass)
+
+    parent = device_registry.async_get_device_by_identifier(
+        (DOMAIN, "uniqueid"), entry.entry_id
+    )
+    assert parent is not None
+
+    child = device_registry.async_get_device_by_identifier(
+        (DOMAIN, child_identifier), entry.entry_id
+    )
+    assert child is not None
+    assert child.via_device_id == parent.id
+
+
 async def test_async_setup_entry_failure(hass: HomeAssistant) -> None:
     """Test a unsuccessful setup entry."""