There are several options. One is to set up your own server and let your family stream from that. Plex is one of the easier ways to do that. But if the Videos aren't too big, you can also upload them to a cloud provider and let your family play them on the ATV using Infuse (which supports Dropbox, Google Drive, and MS Onedrive), or simply on a computer if they have one. Yet another option is to use private Youtube videos.