How to handle MdiChild.OwnedForms FormClosing event

Hello all,

I have an MdiParent with an MdiChild form.  In the MdiChild form, I open a form for which the MdiChild is the Owner.  My code is as follows:

// MdiChild opening form
private void OpenForm()
{
	Form3 frm = new Form3();
	frm.Owner = this;
	frm.Show();
}

// MdiParent's FormClosing
private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
	Properties.Settings.Default.Size = this.Size;
	Properties.Settings.Default.Save();
}

// MdiChild's FormClosing
private void Form2_FormClosing(object sender, FormClosingEventArgs e)
{
	//this condition is rare so we can say that nothing else happens in this function
	if (condition) {//...}
}

// MdiChild OwnedForms's FormClosing
private void Form3_FormClosing(object sender, FormClosingEventArgs e)
{
	if (this.dataSet.HasChanges())
	{
		DialogResult result = MessageBox.Show("Save changes?", MessageBoxButtons.YesNoCancel);
		if (result == DialogResult.Yes)
		{
			UpdateData();
		}
		else if (result == DialogResult.No)
		{
			// just let form close
		}
		else
		{
			e.Cancel = true;
		}
	}
}

When I close the MdiParent, Form3 does not have its FormClosing event triggered.  When I close the MdiChild it works fine.  Any idea of why this is? 

Thanks.