Hopefully this won't gross anyone out, but here it goes! It's very hard to tell the sex of the kittens, but the main thing you are looking for is what looks like two anuses on the girl, and a furry knob in front of the anus on the boys. Sometimes it's very hard to tell what gender they are, especially if they are very furry on their tummies, but the boys will have more fur on the "knob" whereas the girls will be hairless. If the fur gets in the way, you can move it with your finger. From my experiences, the girls will pee on you 9 times out of ten when you brush the hair aside whereas the boys have more bladder control. I wouldn't use this to decide gender, but so far almost every girl has peed on me when i moved the hair whereas i've never had a boy do that! Eeeeeeeeeeewwwww!