WPF Custom Control Containing Custom Child Controls

Question

how do you render child controls contained withing a WPF custom control?

<MyControl>
  <Mycontrol.Children>
     <MyChildControl />
     <MyChildControl />
  </MyConrtol.Children>
</MyControl>

I've created a parent control with basic properties, which renders correctly. I've also created child controls, which also render correctly when implemented in a page, or window. However, when I implement the child controls within the parent control's ObservableCollection, as above, the child controls are not rendered.