Sexing Kittens
Kittens can be sexed from a very young age. It is possible to firmly grip the skin behind their necks (their scruff) and hold onto them gently but firmly on their backs to look at their bottoms.
The length between the anus and the penile opening is longer in males compared to females. The testicles are not really visible in very young kittens but they can be seen as a raised lump between the anus and penile opening.
Female kittens have a little slit whereas male kittens have more of a round hole. If they are tabbies or multicoloured moggies, I have found the little area of fur around the penis is usually a different colour in a little ring.