I have an FXML file for a "wizard" style dialog. It has two "pages" both of which are children of a StackPane, but only one is visible at a time. The first page is in the FXML as a GridPOane child, the second is an AnchorPane via an include, e.g.:
    <StackPane fx:id="stackPane">
      <children>
        <GridPane fx:id="pageOne" ... >...</GridPane>
         <fx:include fx:id="pageTwo" source="secondPage.fxml" visible="false" />
      </children>
    </StackPane>

I hide or show the correct page by checking the id and making that node visible and the other invisible.

With Java 7 (JavaFX 2.2.65) this works correctly. With Java 8u20 the fx:include node has an id of "AnchorPane" instead of the assigned fx:id of "pageTwo"