In order to understand the meaning of association, you should first be aware that there is a difference between the members of your Family Site and the individuals in your tree.
This means that your family members can become members of the site, without us knowing the identity of the corresponding family tree individuals.
It is also possible that the Site Manager himself has not associated himself to the family tree.
We recommend that all of the site members are associated with the family tree, so that we can understand their relationships to other individuals in the tree.
You can read about how to associate members of your site here: