Here is a XAMLToy ready code snippet:

<Grid
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 <Canvas>
        <Path Stroke="Black" StrokeThickness="2" Fill="Blue">
            <Path.Data>
                <GeometryGroup>
                    <EllipseGeometry Center="110 60" RadiusX="50" RadiusY="50" />
                    <EllipseGeometry Center="80 110" RadiusX="50" RadiusY="50" />
                    <EllipseGeometry Center="140 110" RadiusX="50" RadiusY="50" />
                </GeometryGroup>
            </Path.Data>
        </Path>
    </Canvas>
</Grid>

It should render three ellipses but it instead will show one ellipse as if there is only the first child of the GeometryGroup