I have two kittens that are sisters. They are about 12 weeks old right now, and seemingly quite healthy. The last two days, one of the kittens has been doing something very odd, and to be completely honest, awkward. Arya, the smaller one, has been "cleaning" Fiona's genital area, and quite vigorously at that. She just goes at it, and I can't get her to stop. I'll pull her off of Fiona and she'll just go right back to it. Is this normal cat behavior, like it is in children to explore, or is it something I should try to do do something about? Any help would be awesome. These are my first cats I've ever had.