I mean, you can try it. I took a random photo in my library, my self and a friend taking a selfie at a museum. I added the blur and there is no way to make both of us sharp while having the background blurred. Our depths are that different (inches), I suppose. At least with a DSLR you could correct this before taking the picture (by adjusting the composition of the shot). Doing it after the fact with a questionable depth map... not as good.

One could take the depth map and use it to mask off two areas to keep sharp, which would potentially have better-than-real-camera results. The iPhone does not do this, however. You'd have to write your own program to do it.