Multiple HwndHost not getting seperate HWND

I'm rendering video with OpenGL in WPF with a HwndHost-class. It works really well until I create a second instance of my HwndHost-host element. What happens is that the two elements gets the same HWND which renders two videos on the same surface and crashes OpenGL.

Using any in-built video element or Image-element with D3DImage is not an option.

Is there any way two request unique HWNDs from WPF?