I need a little help from experts

I have a hard disk full of movies and a raspberry pi and wireless router are there any idea to stream those movies over wifi router so my brother that he live in the next floor can watch movies on his mobile android or Apple using an account so he can access by username and password.?

You can get PMS to work on a PI - https://forums.plex.tv/discussion/145717/i-have-pms-running-on-raspberry-pi-2/p1 - though it is not for the faint of heart and you will not get any transcoding (so all the movies on that hard disk needs to be compatible with the Plex clients).

@Peter_W said:
You can get PMS to work on a PI - https://forums.plex.tv/discussion/145717/i-have-pms-running-on-raspberry-pi-2/p1 - though it is not for the faint of heart and you will not get any transcoding (so all the movies on that hard disk needs to be compatible with the Plex clients).

Yeah, that’s what I used before I bought a SHIELD. It was hell. It transcoded music just fine, but I couldn’t get a single smooth transcoded video stream. It basically forced me to upgrade.

If you still want to use a Pi, i’d recommend .mp4 as your movie format. Relatively user-friendly, and doesn’t take up too much bandwidth, meaning you can stream it just fine. If .mp4 doesn’t work on a specific device, try getting a multi-format media player, such as VLC or Kodi.
Some alternate routes would be running Plex Media Server on your laptop, or using Plex Cloud, which is a cloud-based server (although you’d most likely have to pay monthly to get the storage you need, so probably not the best option). Or you could just skip Plex altogether and just build a Raspberry Pi NAS (If your brother can get a decent signal from your router). Doesn’t look great, but it works.