Binding combo box in user control does not work but regular combobox works

I have user control that contains a textblock and a combo box as shown below:

<UserControl .... Name="myReusableControl"><TextBlockDockPanel.Dock="Left"x:Name="label">Title:/TextBlock><ComboBoxx:Name="comboBox"></ComboBox></UserControl>

I have added the following the following for the code behind of the user control.

public partial class ctlCombobox : UserControl
    {

    public static readonly DependencyProperty DisplayMemberPathProperty = DependencyProperty.Register("DisplayMemberPath", typeof(string), typeof(ctlCombobox), new FrameworkPropertyMetadata() { BindsTwoWayByDefault = true }); 
    public static readonly DependencyProperty ItemsSourceProperty = DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(ctlCombobox), new FrameworkPropertyMetadata() { BindsTwoWayByDefault = true });          
    public static readonly DependencyProperty SelectedIndexProperty = DependencyProperty.Register("SelectedIndex", typeof(int), typeof(ctlCombobox), new FrameworkPropertyMetadata() { BindsTwoWayByDefault = true });
    public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.Register("SelectedItem", typeof(object), typeof(ctlCombobox), new FrameworkPropertyMetadata() { BindsTwoWayByDefault = true });
    public static readonly DependencyProperty SelectedValuePathProperty = DependencyProperty.Register("SelectedValuePath", typeof(string), typeof(ctlCombobox), new FrameworkPropertyMetadata() { BindsTwoWayByDefault = true });
    public static readonly DependencyProperty SelectedValueProperty = DependencyProperty.Register("SelectedValue", typeof(object), typeof(ctlCombobox), new FrameworkPropertyMetadata(OnSelectedValueChanged) { BindsTwoWayByDefault = true });


    public ctlCombobox()

    {
        InitializeComponent();

        Binding selectedIndexBinding = new Binding("SelectedIndex") { Source = this, Mode = BindingMode.TwoWay };
        Binding itemsSourceItemBinding = new Binding("ItemsSource") { Source = this, Mode = BindingMode.TwoWay };
        Binding displayMemberPathBinding = new Binding("DisplayMemberPath") { Source = this, Mode = BindingMode.OneWay };
        Binding selectedItemBinding = new Binding("SelectedItem") { Source = this, Mode = BindingMode.TwoWay };
        Binding selectedValueBinding = new Binding("SelectedValue") { Source = this, Mode = BindingMode.TwoWay };
        Binding selectedValuePathBinding = new Binding("SelectedValuePath") { Source = this, Mode = BindingMode.TwoWay };

        comboBox.SetBinding(ComboBox.SelectedIndexProperty, selectedIndexBinding);
        comboBox.SetBinding(ComboBox.ItemsSourceProperty, itemsSourceItemBinding);
        comboBox.SetBinding(ComboBox.DisplayMemberPathProperty, displayMemberPathBinding);
        comboBox.SetBinding(ComboBox.SelectedItemProperty, selectedItemBinding);
        comboBox.SetBinding(ComboBox.SelectedValueProperty, selectedValueBinding);
        comboBox.SetBinding(ComboBox.SelectedValuePathProperty, selectedValuePathBinding);
    }


    public IEnumerable ItemsSource
    {
        get { return (IEnumerable)GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }

    [Browsable(true)]
    public int SelectedIndex
    {
        get { return (int)GetValue(SelectedIndexProperty); }
        set { SetValue(SelectedIndexProperty, value); }
    }

    [Browsable(true)]
    public object SelectedItem
    {
        get { return (object)GetValue(SelectedItemProperty); }
        set { SetValue(SelectedItemProperty, value); }
    }

    [Browsable(true)]
    public object SelectedValue
    {
        get { return (object)GetValue(SelectedValueProperty); }
        set { SetValue(SelectedValueProperty, value); }
    }

    [Browsable(true)]
    public string SelectedValuePath
    {
        get { return (string)GetValue(SelectedValuePathProperty); }
        set { SetValue(SelectedValuePathProperty, value); }
    }

I make reference to the control above in my main control as shown below:

<UserControl Name="mainControl" ...>       <DataGrid Name="lvEmployee" ItemsSource="{Binding Path=Employees, Mode=TwoWay}"  <DataGrid.Columns>                <DataGridTextColumn Header="Employee Type" Width="7*" Binding="{Binding Path=EmployeeType.Name}" />                <DataGridTextColumn Header="First Name" Width="8*" Binding="{Binding Path=FirstName}" />                <DataGridTextColumn Header="Middle Name" Width="8*" Binding="{Binding Path=MiddleName}" />                <DataGridTextColumn Header="Last Name" Width="9*" Binding="{Binding Path=LastName}" />             </DataGrid.Columns>         <DataGrid.RowDetailsTemplate><DataTemplate>                    <cc:ctlCombobox x:Name="cmbEmployeeType" 
                 ItemsSource="{Binding Source={x:Reference mainControl}, Path=DataContext.EmployeeTypes}"          
                 DisplayMemberPath="Name" SelectedValuePath="Id"   SelectedValue="{Binding   
                 Path=EmployeeTypeId}"  "></cc:ctlCombobox></DataTemplate></DataGrid.RowDetailsTemplate></DataGrid>	</UserControl>

The issue is the  with cc:ctlComboboxx:Name="cmbEmployeeType". It should function as a look up where it is populated with all  the possible EmployeeTypes. However, when I try to bind to Employee.EmployeeTypeId (datacontext is Employee object),  the combobox is not selected.

I have no error in output. Additionally, the binding works if I use a plain combobox and also my bindings work for textbox user controls inside the datatemplate. I am using the MVVM pattern.