Weird behaviour by one of our cats

Question
This is messed up.  We had 2 cats.  One of them had 4 kittens.  We assumed all of them are girls as there was no visible evidence to suggest otherwise.

Well, both of the adults are female and go into heat periodically, so I am familiar with what being in heat entails.  

Lately the first born kitten (now about 8 months old) has started the same mewling and rubbing and exhibiting the exact same behavior as the two adult females.  Even in so far as to squat and put her butt up in the air. The weird thing is, she/he (honestly we can't tell because of this) has gotten on the back of her aunt (the two adult cats are sisters, one the mom, one the aunt) and has been trying to hump her.  I've even seen her/him biting the back of her aunt's neck while trying to hump her.  This is male cat behavior, YET, she also exhibits all of the signs of being a female cat.  She/he is also obviously in heat.  She/he does squat and put her butt up.  Does anyone know what is going on here?  Do we have a female cat born into a male cats body or vice versa? LOL  I'm just not sure what to make of this..... Please any answers would be greatly appreciated.

Thank You,
Wendy :)

Answer
Wendy,

I'm a little confused, because if the kitten is now 8 months old, then you should be able to tell what sex it is.  If it's a male, you should be able to see testicles that hang down on either side below the anus.  Also, you can tell what sex the kitten is by the anogenital openings and appearance.  If it's a female kitten, the urethra and anus will be very close to one another.  If you flip the kitten over, and look, if female, she will have her anal opening at the base of her tail, and then almost immediately below that, will be another opening, and this is the urethra.  Also, the urethral opening in females looks like a slit, whereas in males, it's more of a circular opening.  In males, if you flip the kitten over and look, the anal opening will also be at the base of the tail.  But the scrotum is located below the anus, and above the back of the hind legs.  The testicles descended at birth, but up until 8-10 wks usually cannot be seen.  However, after 8-10 wks, you should be able to see testicles.  A male cat's penis is immediately below the scrotum and projects behind the cat and is normally not visible because it's contained within the prepuce.  If you have the kitten flipped over, you can gently press along the sides of the urethral opening.  If it's a male, you should be able to get the penis to pop out.  Also, if you feel for testicles, if it's a male, you will definitely be able to feel them!  Also, you should be taking the kittens in right about now for their first series of vaccinations, so when you do that, the vet should be able to tell you the sexes as well.

As for the behavior the kitten is exhibiting that is similar to mounting the female.  It can be because it is a male kitten; but it can also be because the kitten is still a kitten, and is simply playing.  I've had a few kittens of both sexes, and they all exhibited that behavior until I got them neutered/spayed.  I hope you will be getting all the kittens (and adult cats) spayed and neutered.  Otherwise, if that kitten is a male, he could very well impregnate all the females you have as I believe kittens are actually capable of impregnating females between 4-6 months (but I'm not positive on that).  

You can visit these websites as they have some good, basic info about sexing kittens, as well as some pics:

http://www.kitten-rescue.com/sexing_the_kitten.html
http://www.peteducation.com/article.cfm?c=1+2137&aid=923

Savannah