You can have a maximum of ten blogs on newTumbl.
One blog will always be your Primary Blog, and one blog will always be your Active Blog.
Your Primary Blog is not necessarily your Active Blog.
Blogs are not tied together - if you create two blogs, or ten blogs, unless you tell someone that these are all your blogs, no one will know that these blogs belong to your account.
See Your blogs/Blog management in our Help Center for detailed information on multiple blogs.
See Your blogs/Blog basics/Blog selector menu for detailed information on how to select one of your blogs.