Web Custom Control Problem

This code works fine on a form:

VB Code:

Dim t As New Table
        Dim tr As New TableRow
        Dim tc As New TableCell
 
        Dim b As New Button
        b.Text = "Button 1"
 
        tc.Controls.Add(b)
        tr.Cells.Add(tc)
        t.Rows.Add(tr)
 
        tr = New TableRow
        tc = New TableCell
        b = New Button
 
        b.Text = "Button 2"
        tc.Controls.Add(b)
        tr.Cells.Add(tc)
        t.Rows.Add(tr)
 
        PlaceHolder1.Controls.Add(t)

But when I try to do something similar in a Web Custom Control, it doesn't work:

VB Code:

' Page_Load
        Dim b As New Button
        b.Text = "Button 1"
 
        repeat.Controls.Add(b)
 
        b = New Button
 
        b.Text = "Button 2"
        repeat.Controls.Add(b)

VB Code:

' Web Custom Control Render
    Protected Overrides Sub Render(ByVal output As System.Web.UI.HtmlTextWriter)
 
        Dim t As New Table
 
        For Each ctrl As Control In Me.Controls
            Dim tr As New TableRow
            Dim tc As New TableCell
 
            Debug.WriteLine(ctrl.ClientID)
 
            ' The next line causes the problem
            tc.Controls.Add(ctrl)
 
            tr.Cells.Add(tc)
            t.Rows.Add(tr)
 
        Next
 
        t.RenderControl(output)
 
    End Sub

When I use the control on Page_Load, only one button is shown...
Why won't this work?