There are few different ways to watch videos and movies together online in Long-distance relationships. I figure I make a list of ways for people.

Rabb.it - Online Video Streaming Rooms (Free)

This website lets you invite people into a room to stream content, it creates a chat lobby as well so you can talk together inside the room. The downside is it can be laggy with some services. The resolution / quality is worst compared to other methods. This method is best for people who want to browse content like YouTube videos together, but it also can support links to streaming sites like Netflix or general browsing.

Pros
*Streams Netflix & Other Platforms
*Chat rooms that you can fill with dozens of people.
*Can view other websites using the browser to access any site on the internet.

Cons
*Requires sign in
*Quality can be blurry


Plex.TV - Private Home Media Server (Free - Paid version is not needed)

For techy people but offers great quality, control and freedom. This creates a server on your computer, you download the files to your computer place them in a folder and you create your own library of movies, photos and music. You can allow "Remote Connections" using port forwarding on your router to share your content with people outside your home network (LAN). Plex allow streams locally to any device in your home including smart TVs so you can watch movies streamed from your computer. Some people buy dedicated computers for Plex. It is easy to set up and is free, hardest part may be inviting the user to have access to your library and port forwarding your IP on your home router which there are guides for out there.

Pros
*Streams any content including photos, movies and more.
*Can stream as much quality as your network can upload.
*You can share the same content on your home firestick, rokus and smart TVs so you can watch things in bed or other rooms, as long as your server stays online.
*Lot of flexibility about bitrates / quality for people to change if they have bad internet.

Cons:
*May require port forwarding for your router if you are the host, which may not be possible if you are a on controlled network (College, Company etc..). Many guides out there for adding your IP to be forwarded. https://support.plex.tv/articles/200931138-troubleshooting-remote-access/
*Requires all connected users to have an account, then you need to manually give view access to that user so they can see your library.

ManyCam - Skype & Google Hangouts Video (29$/year - 49$/Lifetime There is a free version, but it is quite limited)

This is a weird way, but it works. Both Skype and Hangouts support sharing your screen, so you can play a video on your desktop and it plays to the other person. Problem is both Skype and Hangouts run their screen sharing at 15FPS which makes videos look slow and awful. Most webcam streams play at 30fps. Using ManyCam you can spoof things. ManyCam acts as a secondary web camera you have control of that you add text, filters, youtube videos and such to. It does not replace your web camera. So what you do is set your desktop as your ManyCam output. This makes your desktop play through your web camera on Skype and hangouts. Google and Skype run webcams at 30FPS so it makes watching movies much nicer and tricks them. This is a convoluted method, but may be useful for some so I figure I mention it. I will say quality is watchable, but has similar blurry problems to Rabb.it (although it is better quality if I remember).

Pros
*Works on multiple services like Skype, Discord, Hangouts or anything that uses webcams.
*You can set it up so you can also talk while sharing, even add your face as an overlay and switch between inputs like a twitch streamer.

Cons
*Cost money quality may not be exactly HD depending on the services you use.
*In rare cases, some services block it because it is not true webcam with recognized drivers.
*If you are sharing desktop audio to another person, they will hear themselves in the desktop audio when talking (may be a problem for some) alternative is you can use two apps, one to share video and one to call to avoid this problem.