You don't have to delete your whole account to remove specific data.
Unpair a device
In the parent app, go to Settings, select the device, and tap "Unpair." This immediately removes all of that device's data, including its identifiers and usage history.
If you're moving a child to a new device rather than removing one, see Unpair or move a device to another child.
Delete a child profile
In the child's settings, tap "Delete Profile." This removes all data associated with that child — profile details, paired devices, and usage history.
What stays
Your parent account itself (email and sign-in) remains until you delete the full account.