<Window x:Class="DefaultBehavior_KeyBinding.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<Window.InputBindings>
    <KeyBinding Key="F2" Command="{Binding TestCommand}"/>
</Window.InputBindings>
<Grid>
    <Button Content="Add" Width="100" Height="35" Grid.Row="0" Name="EmptyButton" Click="EmptyButton_Click"/>
</Grid>

public partial class MainWindow : Window
{
    public ICommand TestCommand { get; private set; }
    public MainWindow()
    {
        this.TestCommand = ........some command is attached here...
        InitializeComponent();
        this.DataContext = this;
    }

    private void EmptyTabButton_Click(object sender, RoutedEventArgs e)
    {
        Window childwindow = new Window() { Title = "ChildWindow", Width = 200, Height = 300 };
        childwindow.Show();
    }
}

MainWindow mainWindow;
public Window(MainWindow w)
{
   mainWindow = w;
}

mainWindow.TabPress();

Window childwindow = new Window(this) { Title = "ChildWindow", Width = 200, Height = 300 };
childwindow.Show();

private void EmptyTabButton_Click(object sender, RoutedEventArgs e)
    {
        Window childwindow = new Window() { Title = "ChildWindow", Width = 200, Height = 300 };

        childWindow.InputBindings.AddRange(this.InputBindings);

        childwindow.Show();
    }