Hallo
I want to use plex so that my girlfriend and my sister to be able to view all my videos.
So my question is when I buy the plex pass do they also have the same features as me like mobile sync?
or do they need to buy the pass them self ?
You don’t need Plex Pass to share libraries with other users. Other than that, I don’t really understand what you are asking.
Plex Pass is tied to the user account.
Please use the search feature first before you ask a question 
You would be able to share currently without buying a Plex Pass: Create a New Share
As to mobile sync Plex Pass benefit, this comes from the server. If you enable the setting Allow Sync for their user they will be able to sync content. You’ll find that setting in the Create a New Share FAQ under the heading Set Restrictions if you have your server signed in with a Plex Pass account.
A Plex Pass is not needed at all for any “regular” sharing or streaming functions. It does allow the use of “Plex Home” but that is not needed for what you say you want to do except, maybe, mobile sync. I do not and have never used any sync functions so someone else will need to answer about that. But I did check and mobile sync is listed as a Plex Pass feature so I believe that anyone using it will need a Plex Pass but if you get a Plex Pass yourself and make the people you want to share with members of your Plex Home that may allow them to us the sync functions. I do not know about that for sure but I’m sure that some will either confirm or deny it soon.
