To automatically embed child links in parent pages, edit your transformation scenario transform in Oxygen, click the Parameters tab, and set the rellinks parameter to all. To disable child link embeds, set the value to none.
You can also control rellinks in your ditamap by setting the attribute linking="none" or linking="all" on topicref or topichread elements. This will override, on a case-by-case basis, whatever parameter settings you have in the transform.
In the ditamap, set linking="none" to disable.