The child views get a custom view model, thus cannot inherit anything from their parent (except the model which is injected via binding like you do by binding the DataContext).
You have 2 options here:
1) Use the InterestedIn attribute (see http://catel.catenalogic.com/index.html?creating_a_view_model_that_wat.htm)
2) Use the MessageMediator to publish events that are required for multiple views (see http://catel.catenalogic.com/index.html?message_mediator.htm)
If that is not exactly what you mean, please e-mail the sample to me so I can take a look.