Realism in writing

I think the best compliment I've had about my writing came in an email from my cousin the other day.  We recently re-connected and I told her about my reading and writing blogs.  She went to the writing blog and then emailed me.  She was trying to give me some advice on my "family situation".  She had read a couple of the character profiles and thought I was writing about problems in my family and so she was trying to advise me.  I contacted her and she seemed relieved to find out that what she was reading was part of my book.  I told her it must have been pretty realistic for her to believe it and she told me it was.  Writing is great.