No, Breezi doesn’t currently offer multiple user logins for a site, either simultaneously or asynchronously.
This means that you can’t grant other users access to your site, unless you share your own login data. If you plan on sharing this info, you might want to update your password before doing so. And make sure you only give this information to people you trust.
Also note that only one person can be logged in at the same time. You can make multiple sites if you wish, though you will need a unique email for each site. Check out this question that has a quick explanation on how to use email aliases.
New functionality is being added to Breezi all the time, so you might want to check often our upcoming features.