Well, that's certainly an interesting turn of events. Bravo for the risk, though if you have a significant other that's willing to do this I don't see why you wouldn't be doing the real-life alternative instead. Battle couples are kinda cool, though. *shrug*
Also, I don't see why everyone's getting weirded out by this. You can knock up your friend's character. Doesn't mean you have to, or that it'll come up if you don't want it to. It's just an odd little quirk, an addition that only means something if you intend to use it. As long as you can still slay baddies without having to shag your counterpart every five minutes, there really isn't anything to worry about. So can we move on from the shock of OH MY GOD THIS GAME HAS SEX WITH OTHER PEOPLE WITH IT and move on to the more meaningful tidbits like story and actual gameplay?