I have a Site Collection with ~7 subsites, each which will be utilizing the "Newsfeed" feature. Is there a way to pull all of these subsite newsfeeds into a parent site newsfeed? If not, are the newsfeed posts stored somewhere that I would be able to possibly build a web part to display the most recent posts across these subsites?
In SharePoint, there is a list named Microfeed. It is MySite MicroFeed Persistent Storage List and it is created by the Site Feed feature automatically. It stores the content and data from the default Newsfeed web part at the site home page (e.g. the conversation in Newsfeed ).
The path of Microfeed list:
You can use a Content Search web part and build queries to display data from Microfeed in several sites (and subsites).
Example of queries:
Use FullPostBody managed property to display contents from newsfeed entries.