How to tell the difference between girl and boy kittens?

One way to tell the difference between girl and boy kittens is by looking at their genitalia. Male kittens have a small distance between their anus and genital opening, while female kittens have a larger distance. Another way is to look at the shape of their genital opening - males have a round opening, while females have a vertical slit. It is best to consult a veterinarian for accurate identification.