I recently ran into a setup like this.  The captain of a boat that we installed a Mac Mini and 4 or 5 AppleTVs, had a family share account.  One of the accounts had all the movies on it.  The itunes login that he gave me was linked to that account.  I was able to download all the content from that family share onto the mac mini.  I was able to stream movies with the AppleTV that way, but I was not able to watch them via Home Sharing.  So any downloaded content could not be watched until I changed the AppleID on the AppleTVs and Mac Mini over to the account that actually purchased the movies.  I had to get through to level 2 tech support at Apple in order to figure this out.

Music worked fine though.