Like Netflix I have separate accounts for my family. Is there a way that I share a library that is being shared the main user but not the other users.
No. That is not possible and likely never going to be possible.
One thing to note is if one of your managed users is tied to a regular plex.tv account then they could have the share if the other person allows it.
https://support.plex.tv/articles/203948776-managed-users/
Scroll down to Differences from Regular Plex Accounts
