The property 'Child' is set more than once

I keep getting this error "The property 'Child' is set more than once" when I try to add more than one object to a border i.e. I have an image in a border and I need to put an ellipse inside the border to do collision detection for that specific ellipse and not the entire area. I tried using stackpanel but it did'nt do anything here is my code.

 <Border x:Name="dragborder1"  IsTossable="True" CanRotate="True" HasDropShadowOnTouch="True" CanSize="False" CanMove="True" Canvas.Left="79" Width="866" Height="577" Canvas.Top="96">
                <Image x:Name="piece1" Width="866" Height="577" Stretch="Fill" ClipToBounds="False" SnapsToDevicePixels="False">
                <Image.Clip>
                    <PathGeometry Figures="M292,268c4-24,3-47-6-69c-24-2-47,7-71,1c-28-7-50-26-58-50c-13-41,37-81,79-67c18,6,24,29,41,39c6,4,10-4,10-8
    c0.6-37.784,3.351-76.287,0.5-114H0v302.767C43.442,290.788,87.721,281.405,132,288c12,20-16,29-23,44s-8,38,9,47c31,16,84,0,76-40
    c-3-17-28-32-21-53c37.363-1.384,74.512-0.64,111.646,0.171c0.125-1.391,0.245-2.781,0.354-4.171C286,278,291,273,292,268z"/>
                </Image.Clip>
            </Image>

            <EllipseGeometry x:Name="elips"
                             RadiusX="12" RadiusY="12" />

        </Border>