Keystone supports the ability for a content author to place a component on a page and have that component propagate to all children.
The content author does so by:
1. Placing the component on the page (as normal)
2. Setting the Cascade property from the Edit Component Properties dialog
By default we have not enabled this in Keystone. To do so you will need to add the CascadingRenderings template as the parameter template to the required sublayouts or rendering items.
1. Find your content component definition in /Sitecore/Layouts/Sublayouts or /Sitecore/Layouts/Renderings
2. Add the CascadingRenderings template as the Parameters Template