Blogger vs WordPress Blog

I don't know what you mean by "we". Every WordPress.COM blog has a sole owner. It is the person with the WordPress.COM username account who registered the blog under that username account and a single associated email address, and who is the original Admin of the blogs registered under that username account.

You have to be logged in as Admin http://en.support.wordpress.com/user-roles/#administrator under the exact same username account that registered the blog to access the blog's dashboard. The Admin login link to the dashboard for every blog hosted by wordpress.COM is:

http://NAME_OF_BLOG.wordpress.com/wp-admin/

* You will have to replace "name_of_blog" with the actual blog's name in that URL.

After the blog's owner logs in clicking this link should display all blogs registered under the same username account, including the hidden ones: https://dashboard.wordpress.com/wp-admin/index.php?page=my-blogs&show=hidden

If the blog's owner does not see the blog here http://en.support.wordpress.com/my-blogs/ then they need to follow this guide > http://en.support.wordpress.com/my-blogs/#my-blogs-dashboard-visibility

If the log-in information is lost they need to visit https://en.wordpress.com/wp-login.php?action=lostpassword

If you do not have the required access you need to contact the person who registered the account and site under it and have them transfer the sites to your username account by using this process. http://en.support.wordpress.com/moving-a-blog/#transferring-your-blog-to-another-user-or-account

The owner of the site can transfer the site (and/or upgrades) to another account by adding another username account as an Admin. https://en.support.wordpress.com/user-roles/#administrator

Transferring a Blog to Another WordPress.com User or Account https://en.support.wordpress.com/transferring-a-site-to-another-wordpress-com-account/Transferring upgrades https://en.support.wordpress.com/my-upgrades/#transferring-upgradesChange Credit Card Detailshttps://en.support.wordpress.com/change-credit-card-details/Email notifications https://en.support.wordpress.com/email-notifications/

Source: Change owners of a community blog