Why can't I see someone's friends on Facebook?
You can’t able to see someone's Facebook friends because they have changed their settings to hide their friend list from everyone. This feature makes the profile more private and secure.
You can also enable this setting on your account and make your friend list private. You can apply these changes from the settings of the Facebook application.
But if you would like to see the friend list of the person who’s friends list is already hidden or private then read our blog to know more about this in detail: