The closer we are, the less likely I will show you my work unless I know you have mad editing/critiquing skillz. Of course, I expect that someday I will publish a book and my mommy will read it and think it's super wonderful -- but she thinks everything I've ever done is super wonderful (except my first marriage, but I outgrew that.) And while that sort of validation is very nice and ego-building, that's all it is. And I think ego is detrimental to good writing.
I've used SYW and the "Post Your First Three Sentences" thread, and loved the results because I got good, useable feedback which offers me perspective on how I'm doing and where I need to go. But I wouldn't even post there until I can go no further on my own.
It's not precisely that I am reluctant to share my work because, believe me, I want an audience. It's that I am reluctant to share until I have a good reason for doing so. Either I need help making sure the writing works, or I know it works and I'm ready to sell, or I'm applying to a program that requires a writing sample, etc.
That said, my wife has expressed interest in my work and has read some of it, but certainly not all. I have her read the really polished stuff. It's an intimate act in a sense -- she wants to understand my work, because it's a huge part of my life. It makes sense to show her in that vein. But I don't look to her for advice or input on my work, because she is not a writer.