WPF RadioButton UserControl Group in WinForms

i´ve got an RadioButton UserControl customized by me. I want to use it in a Winform with other 3 WPF RadioButtons, i have pre assigned a GroupName so only one radioButton can be checked. The problem is that when i add the IntegrationElement with my usercontrol inside, the group radioButton does not behave as it should. On the other hand if i use this radioButtons created by my under WPF forms the work perfectly. Can somebody hel me?

My RadioButton

 <UserControl x:Class="WpfApplication1.UserControl2"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="18.8" Width="76.8">
        <UserControl.Resources>
        ...
        </UserControl.Resources>
        <RadioButton Name="radioButton" GroupName="group" Width="72.4" Height="15.6" Margin="1"></RadioButton>
</UserControl>