The "last known parent" property key is undocumented as of today. It's name is DEVPKEY_Device_LastKnownParent and it's value is {83DA6326-97A6-4088-9453-A1923F573B29} 10.

And Win32_PnPEntity has a GetDeviceProperties method that you can use to read any property using it's key name.

So, here is a sample console C# code that dumps it (and the friendly name) for all devices in the system:

foreach (var mo in new ManagementObjectSearcher(null, "SELECT * FROM Win32_PnPEntity").Get().OfType<ManagementObject>())
{
    // ask for 2 properties

    var args = new object[] { new string[] { "DEVPKEY_Device_FriendlyName", "DEVPKEY_Device_LastKnownParent" }, null };
    // or this works too using the PK's value formatted as string
    //var args = new object[] { new string[] { "DEVPKEY_Device_FriendlyName", "{83DA6326-97A6-4088-9453-A1923F573B29} 10" }, null };

    // call Win32_PnPEntity.GetDeviceProperties
    mo.InvokeMethod("GetDeviceProperties", args);

    var mbos = (ManagementBaseObject[])args[1]; // one mbo for each device property key

    var name = mbos[0].Properties.OfType<PropertyData>().FirstOrDefault(p => p.Name == "Data")?.Value;
    if (name != null)
    {
        Console.WriteLine(name);

        var parent = mbos[1].Properties.OfType<PropertyData>().FirstOrDefault(p => p.Name == "Data")?.Value;
        Console.WriteLine(" " + parent);
    }
}