There is no one answer to whether or not you can keep your blog private. It largely depends on the terms of service your blog uses and the privacy policies of the companies hosting your blog.
If your blog uses a self-hosted platform, such as WordPress or Blogger, then you can generally control who has access to your blog’s content and settings. However, if your blog is hosted on a third-party platform, such as Tumblr or Blogger, then the company hosting your blog likely has more control over its privacy policy.
Ultimately, it’s important to read the terms of service and privacy policies of any company you plan to host your blog with to understand their policies regarding private blogs. If you’re unsure whether or not you can keep your blog private, it’s best to speak with a member of the blogging community or contact the hosting company directly.