Your personal data is stored inside what we call a coollection file.https://www.coollector.com/help.html#coollection
You can have multiple coollection files on your computer, one for each member of the family, with his own ratings, etc...
The problem will be with the owned movies, because each member will have to add his owned movies to his coollection file. It's not very convenient if you share all your movies with all the members of the family, but it can be an advantage for example if you have small kids and you want to add only the family movies and cartoons to their coollection, or if there are some movies that not everyone is interested in. If your movies are on disk, it's less of a problem because scanning is very fast.
There are 4 of us in the family and we all have different tastes in movies, actors, actresses, and TV shows.
It looks like you're probably in the case where it's better if each coollection has its own set of movies, even if it's more work.
In the future, I plan to make it possible to work with 2 coollection files at the same time, one for the owned movies, and the other for the ratings, the reviews, etc... The interface of the program would seamlessly combine the 2 coollections. Several persons could use the same coollection for the owned movies, with each person having the right (or not) to modify it.