For the Snape and/or Black challenge on harry100. Review!
Harry doesn't know anything at all about things like love or sex, and it makes him a godsend; because he doesn't see anything wrong about kissing Sirius over Christmas, and kissing Severus during Occlumency. And because he did it, he makes things a little more screwed up and a little more confused and a little more conflicted.
And when both adults confront him about it, he just grins that way he does, and makes them flush. And in the end, he's sitting in Sirius' lap, kissing Severus, with both their hands up his shirt, and everything starts to make sense.
