AFAIK, fragments cannot hold other fragments.
UPDATE
With current versions of the Android Support package — or native fragments on API Level 17 and higher — you can nest fragments, by means of getChildFragmentManager(). Note that this means that you need to use the Android Support package version of fragments on API Levels 11-16, because even though there is a native version of fragments on those devices, that version does not have getChildFragmentManager().