Opacity/Invisibility of a form inside a MDI form

[goocreations]

I have a MDI form containing 2 other forms that I first created via GUI and than manually added to the MDI form.
Form1 = MDI form
Form2 = Form containing a WMP and button
Form3 = Form containing a butoon. This form's opacity is set to 50%, to make it semi invisible.

My MDI Form looks like this

Public Class Form1

    Dim f As New Form2
    Dim g As New Form3

    Public WithEvents b As New Button

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        f.MdiParent = Me
        g.MdiParent = Me

        f.setSize(Me.Width, Me.Height)
        g.setSize(Me.Width, Me.Height)
        f.Show()
        g.Show()

    End Sub

End Class

But when I add Form3 (Dim g as shown above) to the MDI Form it isn't semi-invisible like when I compile Form3 alone, but is 100% visible (as in the screenshot).
Does anyone have a clue how to make it semi-invisible/invisible when I add it to the MDI form??

Thank you!!