As an S.O., I have appreciated my wife's honesty with me - we didn't want a relationship with a lot of secrets. That said, I don't generally think I need to know details she doesn't share with me - it's kind of a two-way street. I understand that she was living a very painful lie in the past, one that I'm amazed at her courage to survive. For instance, I would never have asked her what her "old" name was - it doesn't matter, because that's not who she is. Sure, I've learned it during our relationship, but it is like anything else deeply personal that I might learn in a relationship - it's a sacred trust between her and I. Yet, if I didn't know she spent much of her life living that lie, I would want to know details of her childhood, school experience, relationship with her parents, etc - things that I can see for her would be very painful to share at times. As it is, we talk about these things when the time is right for both of us, but I can focus on the things she's done when she was able to live her identity - instead of the things that were part of the lie. In a sense, if she hid her past from me, she'd still be living a lie, as she'd have to lie to support not telling me about her past - it would still have power over her.
I also think it helps her - because I "know", she doesn't need to worry about receiving mail under the wrong name, having family use the wrong pronouns, etc, and that impacting the relationship. It's still hurtful when those things happen (to her, obviously, and to me because I care about her), but she can have the security that whatever someone who doesn't understand says or does, I'm not leaving her and I will continue to love her - and will continue to see her as she is: as a woman. I would think that the constant vigilance required to keep a S.O. from finding out would be very exhausting and anxiety-producing.
I also think there's a safety issue - what if somehow the other person does find out, after it has been hidden for years? I know that there are a lot of bigots out there that would feel humiliated, embarrassed, and angry if they "found out" the person they are intimate with did not have the expected letter on their birth certificate when they were born - and the deeper the relationship before they found out, the deeper their feelings. Now, I would never say that anyone should have any obligation to tell anyone. Nor would I say that victims are in any way at fault if they don't share, but are found out, and someone does something terrible. The people doing the terrible things are the terrible people. But those are also people you want out of your life as early as possible.
There are people out there who won't leave a relationship after "finding out". I know they are likely in the minority. But I like to think they are worth finding, while the bigots probably aren't worth keeping, certainly not worth lying to keep in a relationship. I'd also say someone that is not an S.O. likely has a whole lot less business knowing about the past than someone who is.
But, admittedly, my personal experience is with a wife who doesn't have a perfect situation, but I also think it would be very hard to create the perfect situation. And I would never pretend that I can understand fully what it is like to experience the pain of someone who is transgendered, particularly about their past. So I can accept that the person living the situation is better equipped than I am to decide what is the right thing to do in their own life.
