I have several projects aimed at a fairly wide variety of audiences:
(1) YA fantasy
(2) children's short story collection (Christian)
(3) intimacy and sex
I've been told the general trend is not to use multiple names, that I need to focus on building my brand. While I understand building a brand, and that building multiple brands is a lot more work, I also feel that these particular markets might not mix well. Some parents of genre #2 might be put off by #1, and some would *definitely* be put off by #3. And it seems that some readers of genre #3 would likely not take seriously an author in #2, and possibly even #1.
I have a book out under my real name in genre #1, and books nearly ready in the other two.)
If I were looking at you as a prospective client, the first thing I'd tell you is to focus. You've got a lot going on here.
I'm assuming the third category is non-fiction, and that's where platform is a requirement. You must have visibility there for any kind of book proposal to have traction.
Thus, pick the name you want to use for that, and start building your platform there.
You don't need platform for novels. I don't know enough about the Christian market to know why they don't like fantasy (for that you'll need to read Rachelle Gardner's invaluable blog---something you should be doing anyway.)
We've talked a lot here on the blog recently about how hard it is to do more than one thing really well. You might want to think about which of these projects is the most important to you, and focus on that.
I'm not sure you need a different name. In this day and age of total transparency, trying to be two people is a whole lot more difficult than it used to be.