Hi!
When we, as readers, have access to an author's point of view, we are also accessing to their feelings. An opinion/point of view are ways to show your standpoint on a topic; and, therefore, your feelings, as you are expressing yourself with your own words.
Age, childhood and Marital Status would not apply because those are so specific cases and an author not all the time talks about them on their writings; however, feelings are always shown in ours expressions, our word-choice, and our textes, in general.
Hope this helps.