I've seen a mother cat that had just given birth. In the first few hours, she was constantly licking her kittens all over, including their genital areas. This licking serves multiple purposes. It not only cleans the kittens but also helps in the bonding process between the mother and her babies. It's an essential part of the early care that mother cats provide to their kittens.
Well, once I was helping at an animal shelter. There was a shy little kitten. When I first had to check if she had any sores in that area, it was a gentle process. I had to be really careful as she was scared. I used a soft swab to do a quick check. It was a new experience for me in terms of handling such a young and timid cat in this way.
In the book 'The Cat Who...' series, the main cat character shows love in various ways, including licking. It has a special relationship with its owner, and the licking is a form of communication and affection within the story.